《As物理历年真题分类汇编》-USB迷|专注于互联网分享

2024年10月24日发(作者：司马琳溪)

Chapter 3 Forces

Section A Multiple Choice

1 A cylindrical block of wood has a cross-sectional area

and weight

. It is totally immersed in water with its axis vertical. The block

experiences pressures

and

at its top and bottom surfaces

respectively.

Which of the following expressions is equal to the upthrust on the

block?

02s)

A (

)

B (

)

C (

)

D (

)

A - W

2 The vector diagram shows three coplanar forces acting on an object at

(02s)

The magnitude of the resultant of these three forces is 1 N.

What is the direction of this resultant?

A ↓ B ↘ C ↙ D ↗

3 A submarine descends vertically at constant velocity. The three forces

acting on the submarine are viscous drag, upthrust and weight.

(02s)

Which relationship between their magnitudes is correct?

A weight < drag

B weight = drag

C weight < upthrust

D weight > upthrust

4 A ruler of length 0.30mis pivoted at its centre. Equal and opposite

forces of magnitude 2.0N are applied to the ends of the ruler, creating

a couple as shown.

(

What is the magnitude of the torque of the couple on the ruler when

it is in the position shown?

(02s)

A 0.23Nm B 0.39Nm C 0.46Nm D 0.60Nm

5 The diagram shows two vectors X and Y.

(02s)

In which vector triangle does the vector Z show the magnitude and

direction of vector X – Y?

6 uniform metre rule of mass 100 g is supported by a knife-edge at the

40 cm mark and a string at the 100 cm mark. The string passes round

a frictionless pulley and carries a mass of 20 g as shown in the

diagram. (02w)

At which mark on the rule must a 50 g mass be suspended so that the

rule balances?

A 4 cm B 36 cm C 44 cm D 96 cm

7 The diagrams represent systems of coplanar forces acting at a point.

The lengths of the force vectors represent the magnitudes of the forces.

(02w)

Which system of forces is in equilibrium?

8 What is meant by the weight of an object?

(02w)

A the gravitational field acting on the object

B the gravitational force acting on the object

C the mass of the object multiplied by gravity

D the object’s mass multiplied by its acceleration

9 Which of the following pairs of forces, acting on a circular object,

constitutes a couple?

(02w)

10 A pendulum bob is held stationary by a horizontal force

. The three

forces acting on the bob are shown in the diagram.

(02w)

The tension in the string of the pendulum is

. The weight of the

pendulum bob is

Which statement is correct?

cos30 B

T= H

sin30 C

cos30 D

sin30

11 Two forces, each of 10 N, act at a point P as shown in the diagram.

The angle between the directions of the forces is 120°.

(03s)

What is the magnitude of the resultant force?

A 5N B 10N C 17N D 20N

12 The diagram shows four forces applied to a circular object.

(03s)

Which of the following describes the resultant force and resultant

torque on the object?

resultant force resultant torque

A zero zero

B zero non-zero

C non-zero zero

D non-zero non-zero

13 A balloon is acted upon by three forces, weight, upthrust and sideways

force due to the wind, as shown in the diagram.

(03s)

What is the vertical component of the resultant force on the balloon?

A 500 N B 1000 N C 10 000 N D 10 500N

14 A force of 5N may be represented by two perpendicular components OY

and OX as shown in the diagram, which is not drawn to scale.

(03w)

OY is of magnitude 3N.

What is the magnitude of OX?

A 2N B 3N C 4N D 5N

15 A hinged door is held closed in the horizontal position by a cable.

Three forces act on the door: the weight

of the door, the tension

in the cable, and the force

at the hinge.

(03w)

Which list gives the three forces in increasing order of magnitude?

16 A spanner is used to tighten a nut as shown.

(03w)

A force

is applied at right-angles to the spanner at a distance of

0.25 m from the centre of the nut. When the nut is fully tightened,

the applied force is 200 N.

What is the resistive torque, in an anticlockwise direction,

preventing further tightening?

A 8Nm B 25Nm C 50Nm D 800Nm

17 Two parallel forces, each of magnitude

, act on a body as shown.

(03w)

What is the magnitude of the torque on the body produced by these

forces?

C 2

D 2

18 The diagram shows a sign of weight 20 N suspended from a pole, attached

to a wall. The pole is kept in equilibrium by a wire attached at point

X of the pole.

(04s)

The force exerted by the pole at point X is F, and the tension in the

wire is 40 N.

Which diagram represents the three forces acting at point X?

19 A uniform beam of weight 50 N is 3.0 m long and is supported on a pivot

situated 1.0 m from one end. When a load of weight W is hung from that

end, the beam is in equilibrium, as shown in the diagram.

(04s)

What is the value of W ?

A 25 N B 50 N C 75 N D 100 N

20 Which two vector diagrams represent forces in equilibrium?

(04w)

A P and Q

B Q and R

C R and S

D S and P

21 A long uniform beam is pivoted at one end. A force of 300 N is applied

to hold the beam horizontally.

(04w)

What is the weight of the beam?

A 300 N B 480 N C 600 N D 960 N

The vector diagram shows three coplanar forces acting on an object

The magnitude of the resultant of these three forces is 1 N.

What is the direction of this resultant?

A↓ B ↘ C↙ D↗

An L-shaped rigid lever arm is pivoted at point P.

(05s)

Three forces act on the lever arm, as shown in the diagram.

What is the magnitude of the resultant moment of these forces about

point P?

A 30 Nm B 35 Nm C 50 Nm D 90 Nm

What is the centre of gravity of an object?

(05s)

A the geometrical centre of the object

B the point about which the total torque is zero

C the point at which the weight of the object may be considered to

act

D the point through which gravity acts

(

)

25 A stone is projected horizontally in a vacuum and moves along a path

as shown. X is a point on this path. XV and XH are vertical and

horizontal lines respectively through X. XT is the tangent to the path

at X. (05w)

Along which direction or directions do forces act on the stone at X?

A XV B XH C XV and XH D XT

26 A uniform beam of weight 100 N is pivoted at P as shown. Weights of

10 N and 20 N are attached to its ends.

(05w)

The length of the beam is marked off at 0.1 m intervals.

At which point should a further weight of 20 N be attached to achieve

equilibrium?

27 The diagram shows four forces applied to a circular object.

(05w)

Which of the following describes the resultant force and resultant

torque on the object?

resultant force resultant torque

A non-zero non-zero

B non-zero zero

C zero non-zero

D zero zero

28 The gravitational field strength on the surface of planet P is one

tenth of that on the surface of planet Q.

(05w)

On the surface of P, a body has its mass measured to be 1.0 kg and

its weight measured to be 1.0 N.

What results are obtained for measurements of the mass and weight of

the same body on the surface of planet Q?

mass on Q weight on Q

A 1.0kg 0.1N

B 1.0kg 10N

C 10kg 10N

D 10kg 100N

29 A force F is applied to a beam at a distance d from a pivot. The force

acts at an angle θ to a line perpendicular to the beam.

(06s)

Which combination will cause the largest turning effect about the

pivot?

F d



A large large large

B large large small

C small small large

D small large small

30 A rigid uniform bar of length 2.4 m is pivoted horizontally at its

(

)

Weights are hung from two points of the bar as shown in the diagram.

To maintain horizontal equilibrium, a couple is applied to the bar.

What is the torque and direction of this couple?

A 40 Nm clockwise B 40 Nm anticlockwise

C 80 Nm clockwise D 80 Nm anticlockwise

The diagrams show three forces acting on a body.

(06s)

In which diagram is the body in equilibrium?

A rigid circular disc of radius r has its centre at X. A number of

forces of equal magnitude F act at the edge of the disc. All the forces

are in the plane of the disc.

(06w)

Which arrangement of forces provides a moment of magnitude 2Fr about

Three coplanar forces, each of magnitude 10 N, act through the same

point of a body in the directions shown.

(06w)

What is the magnitude of the resultant force?

A 0 N B 1.3 N C 7.3 N D 10 N

34 Which force is caused by a pressure difference?

(06w)

A friction

B upthrust

C viscous force

D weight

35 Two 8.0 N forces act at each end of a beam of length 0.60m. The forces

are parallel and act in opposite directions. The angle between the

forces and the beam is 60°.

(07s)

What is the torque of the couple exerted on the beam?

A 2.4Nm B 4.2Nm C 4.8Nm D 9.6Nm

36 What is meant by the weight of an object?

(07s)

A the gravitational field acting on the object

B the gravitational force acting on the object

C the mass of the object multiplied by gravity

D the object’s mass multiplied by its acceleration

37 The diagram shows a plan view of a door which requires a moment of

12Nm to open it.

(07w)

What is the minimum force that must be applied at the door’s midpoint

to ensure it opens?

A 4.8N B 9.6N C 15N D 30N

38 The symbol represents the acceleration of free fall.

(07w)

Which of these statements is correct?

A is gravity.

B is reduced by air resistance.

C is the ratio weight / mass.

D is the weight of an object.

39 Which two vector diagrams represent forces in equilibrium?

(07w)

A P and Q B Q and R C R and S D S and P

40 The diagram shows a diving-board held in position by two rods X and

(01s)

Which additional forces do these rods exert on the board when a diver

of weight 600N stands on the right-hand end?

at X (downwards) at Y (upwards)

A 400N 1000N

B 600N 1200N

C 900N 600N

D 900N 1500N

41 A small ball of weight W is suspended by a light thread. A strong wind

blows horizontally. exerting a constant force F on the ball. The

thread makes an angle



to the vertical as shown.

(01s)

Which equation correctly relates



, F and W?

A cos



= FIW B sin



= FIW

C tan



= FIW D tan



= WIF

42 Two co-planar forces act on the rim of a wheel. The forces are equal

Which arrangement of forces is a couple?

43 Two forces act on a circular disc as shown.

(01s)

Which diagram shows the line of action of the resultant force?

44 What is the definition of force?

(01w)

A the mass of a body multiplied by its acceleration

(

)

B the power input to a body divided by its velocity

C the rate of change of momentum of a body

D the work done on a body divided by its displacement

45 A street lamp is fixed to a wall by a metal rod and a cable.

(01w)

Which vector triangle represents the forces acting t point P?

46 A wheel of radius 0.70m has a couple applied to it as shown.

(01w)

What is the torque on the wheel?

A 0 B 28Nm C 56Nm D 112Nm

47 Two forces X and Y act at a point P as shown. The lengths of the lines

represent the magnitudes of the forces.

(01w)

Which vector diagram shows the resultant R of these two forces?

48 A trailer of weight 30 KN is hitched to a cab at the point X as shown

in the diagram below.

(01w)

What upward force is exerted by the cab on the trailer at the point

A 3Kn B 15kN C 30kN D 60kN

49 A ball of weight W slides along a smooth horizontal surface until it

falls off the edge at time T.

(01w)

Which graph represents how the resultant vertical downwards force F,

acting on the ball, varies with time t as the ball moves from position

X to position Y?

Section B Structured Questions

1 (a) State the conditions necessary for the equilibrium of a body which

is acted up on by a number of forces.

(01w)

1 ............................................................

..............................................................

..................2...........................................

..............................................................

.................................[2]

(b) Three identical springs S

, S

and S

are attached to a point A such

that the angle between any two of the spring is 120°, as shown

in Fig.3.1.

Fig.3.1

The springs have extended elastically and the extensions of S

and

are x. Determine, in terms of x, the extension of S

such that

the system of springs is in equilibrium. Explain your working.

extension of S

= .....................[3]

The lid is held open by means of a horizontal cord attached to the

edge F of the lid. The centre of gravity of the lid is at point

On Fig.3.2 draw

(i) an arrow, labelled W, to represent the weight of the lid,

(ii) an arrow, labelled T, to represent the tension in the cord

acting on the lid,

(iii) an arrow, labelled R, to represet the force of the hinge on

the lid.

[3]

2 (a) Explain what is meant by the

centre of gravity

of an object.

(02s)

..............................................................

..................

..............................................................

......[2]

(b) A non-uniform plank of wood XY is 2.50 m long and weighs 950 N.

Force-meters (spring balances) A and B are attached to the plank

at a distance of 0.40 m from each end, as illustrated in Fig. 3.1.

When the plank is horizontal, force-meter A records 570 N.

(i) Calculate the reading on force-meter B.

reading

= ................ N

(ii) On Fig. 3.1, mark a likely position for the centre of gravity of

the plank.

(iii) Determine the distance of the centre of gravity from the end X

of the plank.

distance

= ............. m[6]

3 (a) Define the moment of a force.

(03w)

..............................................................

...............[2]

(b) State the two conditions necessry for a body to be in equilibrium.

1. ...........................................................

..............................................................

..................

2. ...........................................................

..............................................................

...............[2]

and S

are attached to a disc of diameter

12cm, as shown in Fig.3.1.

The disc is free to rotate about an axis normal to its plane. The

axis passes

through the centre C of the disc.

A lever of length 30cm is attached to the disc. When a force F is

applied at right angles to the lever at its end, equal forces are

produced in S

and S

. The disc remains in equilibrium.

(i) On Fig.3.1, show the firection of the force in each string that

acts on the disc.

[1]

(ii) For a force F of magnitude 150N, determine

1. the moment of force F about the centre of the disc.

moment

= .....................Nm

2. the torque of the couple produced by the forces in the

strings,

torque

= ...................Nm

3. the force in S

force= ...................N[4]

4 (a) Explain what is meant by the

centre of gravity

of a body.

(05w)

..............................................................

..................

..............................................................

..... [2]

(b) An irregularly-shaped piece of cardboard is hung freely from one

point near its edge, as shown in Fig. 2.1.

Explain why the cardboard will come to rest with its centre of

gravity vertically below the pivot. You may draw on Fig. 2.1 if

you wish.

..............................................................

..................

..............................................................

......[2]

5 A rod AB is hinged to a wall at A. The rod is held horizontally by means

of a cord BD, attached to the rod at end B and to the wall at D, as

shown in Fig. 2.1.

(06s)

The rod has weight

and the centre of gravity of the rod is at C. The

rod is held in equilibrium by a force

in the cord and a force

produced

at the hinge.

(a) Explain what is meant by

(i) the

centre of gravity

of a body,

...........................................................

....................... [2]

(ii) the

equilibrium

of a body.

...........................................................

..................

...........................................................

..... [2]

(b) The line of action of the weight

of the rod passes through the

cord at point P.

Explain why, for the rod to be in equilibrium, the force

produced

at the hinge must also pass through point P.

..............................................................

..................

..............................................................

.............. [2]

and

make angles α and β respectively with the rod

and AC = AB, as shown in Fig. 2.1.

Write down equations, in terms of

, α and β, to represent

(i) the resolution of forces horizontally,

...........................................................

......[1]

(ii) the resolution of forces vertically,

...........................................................

......[1]

(iii) the taking of moments about A.

...........................................................

......[1]

我从来就不是一个独立的人，也从没有独立生活过，直到来了加国。

然后发现，有生俱来的独立细胞瞬间苏醒，几乎可以万事不求人，独立自强到令自己刮目相看。

其实是环境使然，因为我也求不到人，举目无亲，求人不如求己。

一个人带着女儿东奔西走，上下求索，差不多半年的时间，生活才算安定下来。

有幸结识了几位华人朋友，圣诞节前第一次聚餐，说起各自的安居经历，无不感叹，加国是个锻炼人的好地方，堪堪把在座的娇娇女都变成了女汉子。

主人是一位大我两岁的姐姐，上得厅堂下得厨房，最是热情好客，令人宾至如归。

席间说起各自的圣诞计划，我打算带女儿去夏威夷度假。

话音刚落，便有两个声音相继表示可以负责我的机场接送。

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“我是早上七点的航班，五点半就得值机，四点半出发，若是让你们送的话，岂不是要跟我一样倒时差了，如果是中午的航班，我就不客气了。”

“任何时侯都不需要客气。朋友是用来干什么的？朋友就是用来相互亏欠的。因为把你当朋友，所以我有求于你的时侯才不会犹豫，反之你有需要的时侯，也理所当然地来求我办事，人

与人之间的感情就是在一次次的相互亏欠互还人情的过程中日渐亲厚的。我巴不得你麻烦我，这样下次我麻烦你的时侯就理直气壮了，否则你从不求我，我怎么好意思去求你，你说是不是这

个理儿？”

我把这当作了一堂宝贵的人情世故课。简单朴实的道理，却蕴含着与人交往的大智慧。

怪不得她周围有这么多的朋友，我很羡慕她为人处事的通透。

从那以后，我学会以另一种方式与人相交，大方索取，大方回报，有欠有还，交情不断。

有位家长临时有事找人代班去图书馆做义工，我正好有时间，立刻响应。之前我们只是恰好在同一个家长群里的点头之交，见面连话都没说过两句。事后，她主动表示有机会一定要替我

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邻居外出期间托我帮他浇花剪草送收垃圾桶，我爽快地同意，等我回国时，也毫不犹豫地请他为我服务。有一天我不在家，监控摄像头通过手机提示我的院门被风刮开了，摇摇晃晃，还

没来得及通知朋友帮我去看一眼，就见邻居走进了画面，拿着工具帮我把松掉的门拴修好，关门离去。我又欠了他一次，没关系，下次包饺子时给他多煮一份。

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脆叫我去她家，品茶煮蓝莓酱。

几年下来，我不再是当初那个独在异乡求助无门的女汉子，如今女汉子仍在，却是同在异乡，出入相友守望相助。

朋友是用来相互亏欠的，投我以桃，报之以李。

2024年10月24日发(作者：司马琳溪)

Chapter 3 Forces

Section A Multiple Choice

1 A cylindrical block of wood has a cross-sectional area

and weight

. It is totally immersed in water with its axis vertical. The block

experiences pressures

and

at its top and bottom surfaces

respectively.

Which of the following expressions is equal to the upthrust on the

block?

02s)

A (

)

B (

)

C (

)

D (

)

A - W

2 The vector diagram shows three coplanar forces acting on an object at

(02s)

The magnitude of the resultant of these three forces is 1 N.

What is the direction of this resultant?

A ↓ B ↘ C ↙ D ↗

3 A submarine descends vertically at constant velocity. The three forces

acting on the submarine are viscous drag, upthrust and weight.

(02s)

Which relationship between their magnitudes is correct?

A weight < drag

B weight = drag

C weight < upthrust

D weight > upthrust

4 A ruler of length 0.30mis pivoted at its centre. Equal and opposite

forces of magnitude 2.0N are applied to the ends of the ruler, creating

a couple as shown.

(

What is the magnitude of the torque of the couple on the ruler when

it is in the position shown?

(02s)

A 0.23Nm B 0.39Nm C 0.46Nm D 0.60Nm

5 The diagram shows two vectors X and Y.

(02s)

In which vector triangle does the vector Z show the magnitude and

direction of vector X – Y?

6 uniform metre rule of mass 100 g is supported by a knife-edge at the

40 cm mark and a string at the 100 cm mark. The string passes round

a frictionless pulley and carries a mass of 20 g as shown in the

diagram. (02w)

At which mark on the rule must a 50 g mass be suspended so that the

rule balances?

A 4 cm B 36 cm C 44 cm D 96 cm

7 The diagrams represent systems of coplanar forces acting at a point.

The lengths of the force vectors represent the magnitudes of the forces.

(02w)

Which system of forces is in equilibrium?

8 What is meant by the weight of an object?

(02w)

A the gravitational field acting on the object

B the gravitational force acting on the object

C the mass of the object multiplied by gravity

D the object’s mass multiplied by its acceleration

9 Which of the following pairs of forces, acting on a circular object,

constitutes a couple?

(02w)

10 A pendulum bob is held stationary by a horizontal force

. The three

forces acting on the bob are shown in the diagram.

(02w)

The tension in the string of the pendulum is

. The weight of the

pendulum bob is

Which statement is correct?

cos30 B

T= H

sin30 C

cos30 D

sin30

11 Two forces, each of 10 N, act at a point P as shown in the diagram.

The angle between the directions of the forces is 120°.

(03s)

What is the magnitude of the resultant force?

A 5N B 10N C 17N D 20N

12 The diagram shows four forces applied to a circular object.

(03s)

Which of the following describes the resultant force and resultant

torque on the object?

resultant force resultant torque

A zero zero

B zero non-zero

C non-zero zero

D non-zero non-zero

13 A balloon is acted upon by three forces, weight, upthrust and sideways

force due to the wind, as shown in the diagram.

(03s)

What is the vertical component of the resultant force on the balloon?

A 500 N B 1000 N C 10 000 N D 10 500N

14 A force of 5N may be represented by two perpendicular components OY

and OX as shown in the diagram, which is not drawn to scale.

(03w)

OY is of magnitude 3N.

What is the magnitude of OX?

A 2N B 3N C 4N D 5N

15 A hinged door is held closed in the horizontal position by a cable.

Three forces act on the door: the weight

of the door, the tension

in the cable, and the force

at the hinge.

(03w)

Which list gives the three forces in increasing order of magnitude?

16 A spanner is used to tighten a nut as shown.

(03w)

A force

is applied at right-angles to the spanner at a distance of

0.25 m from the centre of the nut. When the nut is fully tightened,

the applied force is 200 N.

What is the resistive torque, in an anticlockwise direction,

preventing further tightening?

A 8Nm B 25Nm C 50Nm D 800Nm

17 Two parallel forces, each of magnitude

, act on a body as shown.

(03w)

What is the magnitude of the torque on the body produced by these

forces?

C 2

D 2

18 The diagram shows a sign of weight 20 N suspended from a pole, attached

to a wall. The pole is kept in equilibrium by a wire attached at point

X of the pole.

(04s)

The force exerted by the pole at point X is F, and the tension in the

wire is 40 N.

Which diagram represents the three forces acting at point X?

19 A uniform beam of weight 50 N is 3.0 m long and is supported on a pivot

situated 1.0 m from one end. When a load of weight W is hung from that

end, the beam is in equilibrium, as shown in the diagram.

(04s)

What is the value of W ?

A 25 N B 50 N C 75 N D 100 N

20 Which two vector diagrams represent forces in equilibrium?

(04w)

A P and Q

B Q and R

C R and S

D S and P

21 A long uniform beam is pivoted at one end. A force of 300 N is applied

to hold the beam horizontally.

(04w)

What is the weight of the beam?

A 300 N B 480 N C 600 N D 960 N

The vector diagram shows three coplanar forces acting on an object

The magnitude of the resultant of these three forces is 1 N.

What is the direction of this resultant?

A↓ B ↘ C↙ D↗

An L-shaped rigid lever arm is pivoted at point P.

(05s)

Three forces act on the lever arm, as shown in the diagram.

What is the magnitude of the resultant moment of these forces about

point P?

A 30 Nm B 35 Nm C 50 Nm D 90 Nm

What is the centre of gravity of an object?

(05s)

A the geometrical centre of the object

B the point about which the total torque is zero

C the point at which the weight of the object may be considered to

act

D the point through which gravity acts

(

)

25 A stone is projected horizontally in a vacuum and moves along a path

as shown. X is a point on this path. XV and XH are vertical and

horizontal lines respectively through X. XT is the tangent to the path

at X. (05w)

Along which direction or directions do forces act on the stone at X?

A XV B XH C XV and XH D XT

26 A uniform beam of weight 100 N is pivoted at P as shown. Weights of

10 N and 20 N are attached to its ends.

(05w)

The length of the beam is marked off at 0.1 m intervals.

At which point should a further weight of 20 N be attached to achieve

equilibrium?

27 The diagram shows four forces applied to a circular object.

(05w)

Which of the following describes the resultant force and resultant

torque on the object?

resultant force resultant torque

A non-zero non-zero

B non-zero zero

C zero non-zero

D zero zero

28 The gravitational field strength on the surface of planet P is one

tenth of that on the surface of planet Q.

(05w)

On the surface of P, a body has its mass measured to be 1.0 kg and

its weight measured to be 1.0 N.

What results are obtained for measurements of the mass and weight of

the same body on the surface of planet Q?

mass on Q weight on Q

A 1.0kg 0.1N

B 1.0kg 10N

C 10kg 10N

D 10kg 100N

29 A force F is applied to a beam at a distance d from a pivot. The force

acts at an angle θ to a line perpendicular to the beam.

(06s)

Which combination will cause the largest turning effect about the

pivot?

F d



A large large large

B large large small

C small small large

D small large small

30 A rigid uniform bar of length 2.4 m is pivoted horizontally at its

(

)

Weights are hung from two points of the bar as shown in the diagram.

To maintain horizontal equilibrium, a couple is applied to the bar.

What is the torque and direction of this couple?

A 40 Nm clockwise B 40 Nm anticlockwise

C 80 Nm clockwise D 80 Nm anticlockwise

The diagrams show three forces acting on a body.

(06s)

In which diagram is the body in equilibrium?

A rigid circular disc of radius r has its centre at X. A number of

forces of equal magnitude F act at the edge of the disc. All the forces

are in the plane of the disc.

(06w)

Which arrangement of forces provides a moment of magnitude 2Fr about

Three coplanar forces, each of magnitude 10 N, act through the same

point of a body in the directions shown.

(06w)

What is the magnitude of the resultant force?

A 0 N B 1.3 N C 7.3 N D 10 N

34 Which force is caused by a pressure difference?

(06w)

A friction

B upthrust

C viscous force

D weight

35 Two 8.0 N forces act at each end of a beam of length 0.60m. The forces

are parallel and act in opposite directions. The angle between the

forces and the beam is 60°.

(07s)

What is the torque of the couple exerted on the beam?

A 2.4Nm B 4.2Nm C 4.8Nm D 9.6Nm

36 What is meant by the weight of an object?

(07s)

A the gravitational field acting on the object

B the gravitational force acting on the object

C the mass of the object multiplied by gravity

D the object’s mass multiplied by its acceleration

37 The diagram shows a plan view of a door which requires a moment of

12Nm to open it.

(07w)

What is the minimum force that must be applied at the door’s midpoint

to ensure it opens?

A 4.8N B 9.6N C 15N D 30N

38 The symbol represents the acceleration of free fall.

(07w)

Which of these statements is correct?

A is gravity.

B is reduced by air resistance.

C is the ratio weight / mass.

D is the weight of an object.

39 Which two vector diagrams represent forces in equilibrium?

(07w)

A P and Q B Q and R C R and S D S and P

40 The diagram shows a diving-board held in position by two rods X and

(01s)

Which additional forces do these rods exert on the board when a diver

of weight 600N stands on the right-hand end?

at X (downwards) at Y (upwards)

A 400N 1000N

B 600N 1200N

C 900N 600N

D 900N 1500N

41 A small ball of weight W is suspended by a light thread. A strong wind

blows horizontally. exerting a constant force F on the ball. The

thread makes an angle



to the vertical as shown.

(01s)

Which equation correctly relates



, F and W?

A cos



= FIW B sin



= FIW

C tan



= FIW D tan



= WIF

42 Two co-planar forces act on the rim of a wheel. The forces are equal

Which arrangement of forces is a couple?

43 Two forces act on a circular disc as shown.

(01s)

Which diagram shows the line of action of the resultant force?

44 What is the definition of force?

(01w)

A the mass of a body multiplied by its acceleration

(

)

B the power input to a body divided by its velocity

C the rate of change of momentum of a body

D the work done on a body divided by its displacement

45 A street lamp is fixed to a wall by a metal rod and a cable.

(01w)

Which vector triangle represents the forces acting t point P?

46 A wheel of radius 0.70m has a couple applied to it as shown.

(01w)

What is the torque on the wheel?

A 0 B 28Nm C 56Nm D 112Nm

47 Two forces X and Y act at a point P as shown. The lengths of the lines

represent the magnitudes of the forces.

(01w)

Which vector diagram shows the resultant R of these two forces?

48 A trailer of weight 30 KN is hitched to a cab at the point X as shown

in the diagram below.

(01w)

What upward force is exerted by the cab on the trailer at the point

A 3Kn B 15kN C 30kN D 60kN

49 A ball of weight W slides along a smooth horizontal surface until it

falls off the edge at time T.

(01w)

Which graph represents how the resultant vertical downwards force F,

acting on the ball, varies with time t as the ball moves from position

X to position Y?

Section B Structured Questions

1 (a) State the conditions necessary for the equilibrium of a body which

is acted up on by a number of forces.

(01w)

1 ............................................................

..............................................................

..................2...........................................

..............................................................

.................................[2]

(b) Three identical springs S

, S

and S

are attached to a point A such

that the angle between any two of the spring is 120°, as shown

in Fig.3.1.

Fig.3.1

The springs have extended elastically and the extensions of S

and

are x. Determine, in terms of x, the extension of S

such that

the system of springs is in equilibrium. Explain your working.

extension of S

= .....................[3]

The lid is held open by means of a horizontal cord attached to the

edge F of the lid. The centre of gravity of the lid is at point

On Fig.3.2 draw

(i) an arrow, labelled W, to represent the weight of the lid,

(ii) an arrow, labelled T, to represent the tension in the cord

acting on the lid,

(iii) an arrow, labelled R, to represet the force of the hinge on

the lid.

[3]

2 (a) Explain what is meant by the

centre of gravity

of an object.

(02s)

..............................................................

..................

..............................................................

......[2]

(b) A non-uniform plank of wood XY is 2.50 m long and weighs 950 N.

Force-meters (spring balances) A and B are attached to the plank

at a distance of 0.40 m from each end, as illustrated in Fig. 3.1.

When the plank is horizontal, force-meter A records 570 N.

(i) Calculate the reading on force-meter B.

reading

= ................ N

(ii) On Fig. 3.1, mark a likely position for the centre of gravity of

the plank.

(iii) Determine the distance of the centre of gravity from the end X

of the plank.

distance

= ............. m[6]

3 (a) Define the moment of a force.

(03w)

..............................................................

...............[2]

(b) State the two conditions necessry for a body to be in equilibrium.

1. ...........................................................

..............................................................

..................

2. ...........................................................

..............................................................

...............[2]

and S

are attached to a disc of diameter

12cm, as shown in Fig.3.1.

The disc is free to rotate about an axis normal to its plane. The

axis passes

through the centre C of the disc.

A lever of length 30cm is attached to the disc. When a force F is

applied at right angles to the lever at its end, equal forces are

produced in S

and S

. The disc remains in equilibrium.

(i) On Fig.3.1, show the firection of the force in each string that

acts on the disc.

[1]

(ii) For a force F of magnitude 150N, determine

1. the moment of force F about the centre of the disc.

moment

= .....................Nm

2. the torque of the couple produced by the forces in the

strings,

torque

= ...................Nm

3. the force in S

force= ...................N[4]

4 (a) Explain what is meant by the

centre of gravity

of a body.

(05w)

..............................................................

..................

..............................................................

..... [2]

(b) An irregularly-shaped piece of cardboard is hung freely from one

point near its edge, as shown in Fig. 2.1.

Explain why the cardboard will come to rest with its centre of

gravity vertically below the pivot. You may draw on Fig. 2.1 if

you wish.

..............................................................

..................

..............................................................

......[2]

5 A rod AB is hinged to a wall at A. The rod is held horizontally by means

of a cord BD, attached to the rod at end B and to the wall at D, as

shown in Fig. 2.1.

(06s)

The rod has weight

and the centre of gravity of the rod is at C. The

rod is held in equilibrium by a force

in the cord and a force

produced

at the hinge.

(a) Explain what is meant by

(i) the

centre of gravity

of a body,

...........................................................

....................... [2]

(ii) the

equilibrium

of a body.

...........................................................

..................

...........................................................

..... [2]

(b) The line of action of the weight

of the rod passes through the

cord at point P.

Explain why, for the rod to be in equilibrium, the force

produced

at the hinge must also pass through point P.

..............................................................

..................

..............................................................

.............. [2]

and

make angles α and β respectively with the rod

and AC = AB, as shown in Fig. 2.1.

Write down equations, in terms of

, α and β, to represent

(i) the resolution of forces horizontally,

...........................................................

......[1]

(ii) the resolution of forces vertically,

...........................................................

......[1]

(iii) the taking of moments about A.

...........................................................

......[1]

我从来就不是一个独立的人，也从没有独立生活过，直到来了加国。

然后发现，有生俱来的独立细胞瞬间苏醒，几乎可以万事不求人，独立自强到令自己刮目相看。

其实是环境使然，因为我也求不到人，举目无亲，求人不如求己。

一个人带着女儿东奔西走，上下求索，差不多半年的时间，生活才算安定下来。

有幸结识了几位华人朋友，圣诞节前第一次聚餐，说起各自的安居经历，无不感叹，加国是个锻炼人的好地方，堪堪把在座的娇娇女都变成了女汉子。

主人是一位大我两岁的姐姐，上得厅堂下得厨房，最是热情好客，令人宾至如归。

席间说起各自的圣诞计划，我打算带女儿去夏威夷度假。

话音刚落，便有两个声音相继表示可以负责我的机场接送。

我和这里的许多老外一样，早在订机票的同时就租好了机场的昼夜停车，自驾往返机场。于是婉言谢绝了朋友的好意。

“下次不许再这样了啊！知道你是不想给人添麻烦，但你知不知道我们就是喜欢被麻烦呀？”主人心直口快地埋怨道。

“我是早上七点的航班，五点半就得值机，四点半出发，若是让你们送的话，岂不是要跟我一样倒时差了，如果是中午的航班，我就不客气了。”

个理儿？”

我把这当作了一堂宝贵的人情世故课。简单朴实的道理，却蕴含着与人交往的大智慧。

怪不得她周围有这么多的朋友，我很羡慕她为人处事的通透。

从那以后，我学会以另一种方式与人相交，大方索取，大方回报，有欠有还，交情不断。

一次班，我欣然接受，你来我往的便成了朋友，更是将相互代班发扬成了传统。

脆叫我去她家，品茶煮蓝莓酱。

几年下来，我不再是当初那个独在异乡求助无门的女汉子，如今女汉子仍在，却是同在异乡，出入相友守望相助。

朋友是用来相互亏欠的，投我以桃，报之以李。

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