Chapter 7

Chapter 7

Dynamics

Paper 1

Each question is followed by four options. Choose the best answer for each question.

1When a basketball player throws a ball up towards the hoop, the ball will drop down after several seconds. This happens because of

A frictional forceB electrostatic force

C magnetic force

D gravitational force

2

What are the forces that are acting on the child in the activity shown in the figure above?

I Frictional forces

II Pulling forces

III Pushing forces

IV Gravitational forces

A I and III only

B II and IV only

C I, III and IV only

D I, II, III and IV

3

How are the activities shown in figure (a) and (b) different?

A Different forces are used to move the trolleys

B Friction acts in (a) but not in (b)

C The trolley moves in (b) but stays in the same position in (a)

D Gravity acts in (b) but not in (a)

4A spherical shaped plasticine ball was dropped from the top of a table. It was observed that the ball was flattened. What can your infer from this activity?

A A force always act on an object

B A force speeds up the motion of an object

C A force slows down the motion of an object

D A force changes the shape of an object

5A salesman rang the electric doorbell of a house for the occupants to come out. What are the forces involved when he rang the bell?

I Gravitational force

II Electrical force

III Magnetic force

IV Pushing force

A I and III only

B II and IV only

C II, III and IV only

D I, II, III and IV

6 A force of 5 N extends a spring by 4 cm. How much force will extend the spring 10 cm?

A 1.25 N

B 12.5 N

C 125 N

D 1250 N

7

What is the original length in cm, l, of the spring shown in the figure above?

A 3 cm

B 5 cm

C 7 cm

D 9 cm

8A force is measured in

A newton metres

B joules

C watts

D newtons

9The extension of a spring can be used to measure the magnitude of force if

A the spring is not rusted

B the elastic limit of the spring has not been exceeded

C the load does not exceed 10 N

D the original length of the spring is more than 3 cm

10

Force (N)0.30.60.91.2

Extension (cm)W81216

The table above shows the results of an experiment carried out to study the relationship between the extension of a spring and the force that stretched the spring. What does W represent?

A 0 cm

B 2 cm

C 4 cm

D 5 cm

11 In which of the following situations is friction an advantage?

I Using chalk to write on a blackboard

II When a person is climbing up the stairs

III When playing football

IV When an aeroplane is flying

A I and III only

B II and IV only

C I, II and III only

D I, II, III and IV

12 Which of the following vehicles experiences the least amount of friction when moving at its top speed?

A Oil tankers

B Army tanks

C Electric trains

D Hovercraft

13Which feature in a car enables it to reduce friction?

I It has an aerodynamic shape

II Its moving parts are lubricated

III It has asbestos lining on the brake pads

IV It has tread on the rubber tyres

A I and II only

B II and IV only

C I, II and III only

D I, II, III and IV

14Why is friction a problem?

I Wears out contact surfaces

II Produces unwanted heat

III Slows down moving parts

IV Enables a car to accelerate

A I and II only

B II and IV only

C I, II and III only

D I, II, III and IV

15Why does a spherical object encounter less friction compared to a rectangular object, when in contact with another surface?

A Spherical objects have no edges

B Spherical objects reduce the contact areas

C Tyres have spherical surfaces

D Spherical surfaces are smooth

16A student carries a bag weighing 10 kg from the floor and places it on a shelf, which is 1.5 m high. How much work was done? (1 kg = 10 N)

A 10 Nm

B 15 Nm

C 150 Nm

D 1500 Nm

17 Mrs Maniam pushes her shopping cart to her car. The frictional force between her shopping cart and the ground is 360 N. If the work done by her is 900 Nm, calculate the distance she has moved.

A 0.2 m

B 2.5 m

C 20 m

D 25 m

18In which of the following situations is work not done?

I Holding a pen

II Writing notes in a book

III Studying the notes in a science book

IV Setting up a neutralisation experiment in the laboratory

A I and III only

B II and IV only

C I, II and III only

D I, II, III and I

19

In the figure above, what is the resistance that the buffalo had to overcome if work done by the buffalo is 32 kJ?

A 4 N

B 40 N

C 400 N

D 4000 N

20A young boy is pushing his tricycle around the porch. In which of the following situations will he do more work?

A If he completes only half a round

B If he puts his toys in the basket of his tricycle before pushing it

C If he runs instead of walk

D If he crawls instead of runs

21Which of the following formulae should we use to calculate power?

Aforce x time

distance

Bforce x time x distance

Cforce + distance

time

Dforce x distance

time

22A lift carried a load of 2 500 kg of cement from the ground to the top of a building which is 50 m high. If the lift took 50 seconds to reach the top of the building, calculate the power generated by the lift.

A 250 W

B 2 500 W

C 25 000 W

D 250 000 W

23

BoyWeight (kg)Time (s)

Azmi

5533

Allan 5235

Ah Meng 6041

Arun6338

The table above shows the time taken by four boys to run up the stairs. Which boy generated the most power?

A Azmi

B Allan

C Ah Meng

D Arun

24Which of the following units can be used to express power?

I Kilowatts

II Newtons

III Watts

IV Joules

A I and III only

B II and IV only

C I, II and III only

D I, II, III and IV

25Why are forces important in our daily life?

I Forces enable us to do work

II Forces enable us to change the speed of objects

III Forces enable vehicles to move and stop

IV Forces create life

A I and III only

B II and IV only

C I, II and III only

D I, II, III and IV

Paper 2

1.Underline the correct S.I unit for Force?

2.Underline the correct answers below to explain how a spring balance works.

The (greater / smaller) the gravitational force, the (longer / shorter) the spring is stretched or compressed.

3.The diagram below shows an activity to measure the magnitude of a force.

.

Record the readings of the spring balance X and Y in the table below based on the diagram above.

Readings of the spring balanceMagnitude of force (N)

X

Y

4.The diagram below shows a bus moving on a wet and slippery road.

Underline the correct answer in the statement below to suggest one way to avoid the bus from skidding off the road.

To avoid the bus from skidding off the road, the driver must use tyres with a rougher surface to (increase / decrease) friction.5. The diagram below shows a boy pulling a wooden block on a table.

Underline the correct answer in the statement below to suggest one way to reduce friction between the surface of the wooden block and the table.

(Sand / Grease) can be use to reduce friction between the surface of the wooden block and the table.

6. Tick () in the correct boxes below, to show the correct examples of the application of friction in daily life.

7.Tick () in the correct boxes below to show work is done.

8.Underline the correct S.I unit of work.

9.The diagram below shows a worker pulling a box with a weight of 300N over a distance of 3 m.

Using the formula above, the work done is:

=300N x 3m

=900Nm

=900Joule

A worker pushes a box with a weight of 250N over a distance of 2m.

Calculate the work done using the same example given above

Work done= Force x Distance

=

=

10. State the meaning of power.

Power is the rate of doing ____________.

11. Underline the correct S.I unit of power.

12. A worker moves a load of 500N over a distance of 2meters in 2 second.

Using the formula above, the power is

=Force x Distance

Time

=500N x 2m

2s

=1000Nm

2s

=500W

Sani pushes a wheelbarrow with a force of 600N over a distance of 3 meters in 15 seconds.

Calculate the power using the same example given above.

Power

=Work done

Time

=Force x Distance

Time

=

=

Chapter 7Dynamics (form 2)

Paper 1

1D2C3A4D5C6B7C8D9B10C

11C12D13A14C15B16C17B18A19B20B

21D22C23A24A25C

Answer scheme

1.Underline the correct S.I unit for Force?

2.Underline the correct answers to explain how a spring balance works.

The (greater / smaller) the gravitational force, the (longer / shorter) the spring is stretched or compressed.

3.The diagram below shows an activity to measure the magnitude of a force.

.

Record the readings of the spring balance X and Y in the table below based on the diagram above.

Readings of the spring balanceMagnitude of force (N)

X8.5N

Y5.5N

4.The diagram below shows a bus moving on a wet and slippery road.

Underline the correct answer in the statement below to suggest one way to avoid the bus from skidding off the road.

To avoid the bus from skidding off the road, the driver must use tyres with a rougher surface to (increase / decrease) friction.5. The diagram below shows a boy pulling a wooden block on a table.

Underline the correct answer in the statement below to suggest one way to reduce friction between the surface of the wooden block and the table.

(Sand / Grease) can be use to reduce friction between the surface of the wooden block and the table.

6.Tick () in the correct boxes below, to show the correct examples of the application of friction in daily life.

7.Tick () in the correct boxes below to show work is done.

8. Underline the correct S.I unit of work.

9. The diagram below shows a worker pulling a box with a weight of 300N over a distance of 3 m.

Using the formula above, the work done is:

=300N x 3m

=900Nm

=900Joule

A worker pushes a box with a weight of 250N over a distance of 2m.

Calculate the work done using the same example given above

Work done= Force x Distance

=250N x 2m

=500Nm

=500Joule

10. State the meaning of power.

Power is the rate of doing work.

11. Underline the correct S.I unit of power.

12. A worker moves a load of 500N over a distance of 2meters in 2 second.

Using the formula above, the power is

=Force x Distance

Time

=500N x 2m

2s

=1000Nm

2s

=500W

Sani pushes a wheelbarrow with a force of 600N over a distance of 3 meters in 15 seconds.

Calculate the power using the same example given above.

Power

=Work done

Time

=Force x Distance

Time

=600N x 3m

15s

=1800Nm

15s

=120W

(a)

(b)

Metre Kilogram Newton Second

Metre Kilogram Newton Second

(

(

NewtonWattJoule

300N

3 m

Work done= Force x Distance

2m

250N

NewtonWattJoule

300N

3 m

Work done= Force x Distance

2m

250N

Joule Watt Volt

500N

2 meters

Power=Work done

Time

600N

3meters

Joule Watt Volt

500N

2 meters

Power=Work done

Time

600N

3meters