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CHAPTER 7 DYNAMIC
S C I E N C E M O D U L E F O R M 2
Page 1
FORCE
A force is a ___________ or a ___________
Type of force
Electric force
Gravitational force
Electromagnetic force
Effect of force
Change in
direction
Changes in
speed
Can move
stationary object
Measurement of force
Unit of force is ______________
Application of Work
Work is said to be done when a force causes an object to
move in the direction
Work (J) = Force (N) x distance (m)
= Nm
Application of Power
Power (W) = Force (N) x distance (m)
time (s)
=watt (W)
CHAPTER 7 DYNAMIC
S C I E N C E M O D U L E F O R M 2
Page 2
Exercise 7.1 Understanding Force
1. (a) Name the forces shown in Diagram 1.1.
(b) Diagram 1.2 shows a girl playing hockey.
Diagram 1.2
(i) ………………………………….. (ii) …………………………………..
(iii) ………………………………….. (iv) …………………………………..
Diagram 1.1
CHAPTER 7 DYNAMIC
S C I E N C E M O D U L E F O R M 2
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State two effects of force on the ball when the girl hits the ball with a hockey stick.
(i) …………………………………………………………………………………………………….
(ii) …………………………………………………………………………………………………….
2. The diagram shows some situations where force is applied.
(a) What is a force?
______________________________________________________________________
(b) State the effect of force in J, K, L and M.
i. J : _________________________________________________________________
ii. K : ________________________________________________________________
iii. L : _________________________________________________________________
iv. M : ________________________________________________________________
(c) Name two types of force.
i. __________________________ ii. _________________________________
CHAPTER 7 DYNAMIC
S C I E N C E M O D U L E F O R M 2
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Exercise 7.2 Measurement of Force
1. The diagram shows a set-up of an experiment to investigate the relationship between the
extension of the spring and the force the acting on it. Weight of 10N each were placed on
the pan and the extension of the spring was noted.
The following table shows the results of the investigation.
Force (N) 0 10 20 30 40 50 60
Extension (cm) 0 3 6 9 12 15 18
(a) What can be used to measure force?
______________________________________________________________________
CHAPTER 7 DYNAMIC
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(b) Using the data in the table, draw straight line to show the relationship between the
extension and the force on the spring.
(c) What can be inferred from the graph in (b)?
______________________________________________________________________
(d) Predict the extension of the spring if a 70N weight was placed on the pan.
______________________________________________________________________
(e) What would happen if 200N weight was placed on the pan?
______________________________________________________________________
CHAPTER 7 DYNAMIC
S C I E N C E M O D U L E F O R M 2
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2. Diagram 1 shows the apparatus set up to investigate the extension of a spring. The result
of the experiment is shown in Table 1.1.
Diagram 1
Mass (g) Extension of spring (cm)
0 0
10 0.5
20 1.0
30 1.5
40 2.0
(a) State the relationship between the mass and the extension of the spring.
_______________________________________________________________________
(b) Plot a graph to show the mass against the extension of the spring.
CHAPTER 7 DYNAMIC
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(c) What is the extension of the spring if the load is 60N?
_______________________________________________________________________
(d) What is the conclusion of the experiment?
_______________________________________________________________________
CHAPTER 7 DYNAMIC
S C I E N C E M O D U L E F O R M 2
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3. Diagram 2 shows an experiment carried out by a student in the laboratory.
Diagram 2
(a) (i) Name the tool used to measure force in Diagram 2.
__________________________________________________________________
(ii) What is the unit for the force measured?
___________________________________________________________________
(b) The graph in Diagram 2 shows a straight line. What does it mean?
______________________________________________________________________
(c) Based on the graph in Diagram 2, how much force is needed to pull the spring if the
extension is
(i) 4 cm = _________________________________________________________
(ii) 10 cm = _________________________________________________________
CHAPTER 7 DYNAMIC
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(d) Determine the extension of the spring if the force acting on it is
(i) 1.5 N = __________________________________________________________
(ii) 5.5 N = __________________________________________________________
(e) What will happen to the spring if too much weight is put on the pan?
______________________________________________________________________
4. Diagram below shows the set –up of apparatus used in an investigation. Different loads are
hung on the spring . Table shows the results of the investigation.
(a) What is the aim of this experiment?
______________________________________________________________________
(b) State a hypothesis of the experiment.
______________________________________________________________________
(c) State the i
(i) manipulated variable : _________________________________________________
(ii) responding variable: _________________________________________________
(iii) constant variable: ________________________________________________
Load (N) 2 4 6 8
Extension of
spring (cm)
1.0 2.0 3.0 4.0
CHAPTER 7 DYNAMIC
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(d) Draw a graph of the extension of spring against load in the space given.
(e) Based on the graph, predict the extension of the spring when a force of 12N is applied
on the spring?
______________________________________________________________________
(f) Make a relationship between load and the extension of spring.
______________________________________________________________________
(g) Can the spring be used to measure force? Give reasons.
______________________________________________________________________
CHAPTER 7 DYNAMIC
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5. Diagram 3.1 shows a wooden block being pulled on a table top.
(a) Name the forces acting on the wooden block. i. ___________________________________________________________________
ii. ___________________________________________________________________
(b) Using , draw the direction of the frictional force acting on the wooden block in the box
provided in Diagram 3.1.
(c) What will happen to the reading of the spring balance if the same wooden block is pulled along a piece of sand paper? ______________________________________________________________________
(d) Diagram 3.2 shows a man pushing a box towards the wall.
Wooden block
Smooth table top
Spring balance
Diagram 3.1
Wall
Box
5 m
Diagram 3.2
CHAPTER 7 DYNAMIC
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(i) Suggest one way on how he can reduce the force needed to push the box.
___________________________________________________________________
(ii) If the force needed to push the box is 300 N. Calculate the work done by the man in pushing the box towards the wall.
6 Diagram 4 shows an experiment to study frictional force on different surface. Table
1.1 shows the reading of the experiment on the different types of surfaces.
Type of surfaces Reading of spring balance (N)
Smooth plank 5
Rough plank 7
On the marbles 2
On the pencils 2
Coated with grease 3
TABLE 1.1
(a) Mark the direction of frictional force in Diagram 4
(b) What can you conclude from this activity?
_____________________________________________________________
(c) State one example where the frictional force is applied in our daily life.
_____________________________________________________________
Wooden block Wooden
block Spring balance
Diagram 4
CHAPTER 7 DYNAMIC
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7. Diagram 5 shows an experiment to determine the magnitude of frictional force on different
types of surfaces. When the wooden block is pulled along the glass surface, the force
applied is 10N.
Diagram 5
(a) What is the aim of the experiment?
______________________________________________________________________
(b) State the variables of the experiment.
a. Constant variable :
____________________________________________________
b. Manipulated variable :
_________________________________________________
c. Responding variable :
_________________________________________________
(c) What is the magnitude of the frictional force when the wooden block is pulled along the
sand paper?
______________________________________________________________________
(d) State the relationship between the type of surface and the magnitude of frictional force.
______________________________________________________________________
(e) What is the conclusion of the experiment?
______________________________________________________________________
(f) Based on the Diagram 5, state one way to reduce friction.
______________________________________________________________________
CHAPTER 7 DYNAMIC
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8.
(a) Based on the observation in situation A and situation B, state the difference in the friction
faced by the worker during the process of pulling the load of 50kg.
______________________________________________________________________
______________________________________________________________________
(b) What inference can be made based on situation A and situation B?
______________________________________________________________________
(c) State a hypothesis based on your observation in the above diagram.
______________________________________________________________________
(d) What is the aim of this experiment ?
______________________________________________________________________
CHAPTER 7 DYNAMIC
S C I E N C E M O D U L E F O R M 2
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9. (a) Diagram 6.1 shows a man pulling a load of 60kg on two different surfaces.
Diagram 6.1
(i) Based on Diagram 6.1, state the difference in the friction faced by the man when he
was pulling the load in situation P and situation Q.
___________________________________________________________________
___________________________________________________________________
(ii) What is the inference that can be made based on situation P and situation Q in
Diagram 6.1?
___________________________________________________________________
(iii) State one hypothesis based on Diagram 6.1.
___________________________________________________________________
(b) Diagram 6.2 shows an experiment to determine the types of surfaces which affect the
magnitude of frictional force.
Diagram 6.2
CHAPTER 7 DYNAMIC
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Based on Diagram 6.2, record the readings of the spring balance in Table 6.3
Surface Reading of spring balance (N)
P
Q
R
Table 6.3
(c) Based on reading in Table 6.3, draw a bar chart to show the readings of the spring
balance on different surfaces.
(d) State the variables of the experiment.
Constant variable
Manipulated variable
Responding variable
(e) Based on Diagram 6.2, state the operational definition of frictional force.
_____________________________________________________________________
CHAPTER 7 DYNAMIC
S C I E N C E M O D U L E F O R M 2
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10. (a) Diagram 7.1 shows a box being pushed on two different surfaces. The force needed to
push the box is a stated in the diagram.
Diagram 7.1
(i) Make an inference based on your observation in Diagram 7.1
___________________________________________________________________
(ii) Make a hypothesis based on your observation.
___________________________________________________________________
(b) An experiment was carried out to investigate on situation (a). The apparatus set up was
as shown in Diagram 7.2.
Diagram 7.2
CHAPTER 7 DYNAMIC
S C I E N C E M O D U L E F O R M 2
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(i) Based on Diagram 7.2, record the readings of the spring balance in table below.
Surface Reading of spring balance (N)
Rubber sheet
Wooden plank
Glass sheet
(ii) By using the readings in the table (b)(i), construct a bar chart to show the spring
balance reading for the different surfaces.
(iii) State the variables involved in this experiment.
Manipulated variable : _________________________________________________
Responding variable : _________________________________________________
Constant variable : ____________________________________________________
(iv) State the operational definition of frictional force in this experiment.
___________________________________________________________________
(v) What will the reading of spring balance be if a layer of grease is spread on the
surface of the wooden plank?
___________________________________________________________________
CHAPTER 7 DYNAMIC
S C I E N C E M O D U L E F O R M 2
Page 19
Exercise 7.3 Application of Frictional Force
1. The diagram shows some situations.
(a) What is frictional force?
______________________________________________________________________
(b) State ways of reducing friction for the situations in the diagram.
i. P : ________________________________________________________________
ii. Q : ________________________________________________________________
iii. R : ________________________________________________________________
(c) i. State an advantage of friction.
___________________________________________________________________
ii. State a disadvantages of friction.
___________________________________________________________________
CHAPTER 7 DYNAMIC
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2. Diagram 1.1 shows some methods used to reduce friction.
(a) Name method P, Q, and R on Diagram 2.1.
P : ___________________________________________________________________
Q : ___________________________________________________________________
R : ___________________________________________________________________
(b) Diagram 1.2 shows some used tyres.
i. What has happened to the surfaces of the tyres?
__________________________________________________________________
P: ……………………….. Q: ……………………….. R: ………………………..
Diagram 1.1
Diagram 1.2
CHAPTER 7 DYNAMIC
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Page 21
ii. Explain your answer in (b)(i).
__________________________________________________________________
(c) Diagram 1.3 shows two persons walking.
i. State one advantage of friction in this situation.
__________________________________________________________________
ii. State one disadvantage of friction in this situation.
__________________________________________________________________
3. (a) What is frictional force?
______________________________________________________________________
(b) Diagram 2 shows a man walking on a wet and smooth floor.
Suggest one possible cause for the man to slip when walking on a wet and smooth floor.
_________________________________________________________________________
Diagram 1.3
CHAPTER 7 DYNAMIC
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(c) State two disadvantages of friction.
______________________________________________________________________
______________________________________________________________________
4. The diagram given shows the set-up of apparatus for an investigation.
(a) What is the manipulated variable in the investigation to study how different types of
surfaces affect frictional force?
______________________________________________________________________
(b) Give one type of surface which will increase the reading of spring balance.
______________________________________________________________________
(c) What conclusion can you make from this experiment?
______________________________________________________________________
(d) How can you
(i) increase the reading of spring balance without changing the glass surface?
__________________________________________________________________
(ii) decrease the reading of spring balance?
___________________________________________________________________
CHAPTER 7 DYNAMIC
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5. The diagrams A and B below show a student running up two different sloping surfaces.
Assume that both surfaces have the same angle of inclination.
(a) Based on your observations of diagrams A and B above, on which slope can the student
run up faster?
______________________________________________________________________
(b) What inference can you make based on diagrams A and B?
______________________________________________________________________
(c) State a hypothesis based on your observations of diagrams A and B.
______________________________________________________________________
(d) What can the boy in Diagram B do to help him run up the slop faster?
______________________________________________________________________
CHAPTER 7 DYNAMIC
S C I E N C E M O D U L E F O R M 2
Page 24
Exercise 7.4 Application of Work and Power
1. A worker pushes a sack of rice using a trolley to the shop as shown in Diagram 1.1.
(a) If the frictional force between the trolley and the ground is 500 N, calculate the work done by the worker.
(b) A boy tries to push the sack of rice but the sack is too heavy for him to move.
i. Did the small boy do any work?
___________________________________________________________________ ii. Why?
___________________________________________________________________
Diagram 1.1
CHAPTER 7 DYNAMIC
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(c) The worker carries a sack of rice weighing 50 kg upstairs. If the mass of the man is 65 kg, calculate the work done in Diagram 1.2.
(1 kg = 10 N)
(d) The worker takes 5 minutes to complete the work in (c). Calculate his power.
2. Diagram 2.1 shows a boy pushing a wall.
Diagram 1.2
CHAPTER 7 DYNAMIC
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(a) (i) Is there a force acting on the wall?
___________________________________________________________________
(ii) Does the boy do any work?
___________________________________________________________________
(iii) Give one reason for your answer in (a) (ii).
___________________________________________________________________
Diagram 2.2 shows a worker dragging a sack of stones with a force of 100N. If the sack of
stones is dragged for 10m in 5 seconds, calculate
(b) The work done
(c) The power of the worker
CHAPTER 7 DYNAMIC
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3. The diagram below shows a 10 kg box being lifted off the ground and placed on a table. It
was then pushed along the table with a force of 70 N through a distance of 1.2 m. [g= 10 N
kg-1].
(a) When was work done against gravity?
______________________________________________________________________
(b) When was work done against frictional force?
______________________________________________________________________
(c) Calculate the work done in lifting the box.
(d) Calculate the work done in pushing the box.
CHAPTER 7 DYNAMIC
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(e) Calculate the power used to lift the box if it takes 5 s to lift the box and place it on the
table.
(f) Calculate the power used to push the box if it takes 4 s to push it 1.2m along the table.
4. Diagram 3 shows a man running up the stairs.
Diagram 3.
CHAPTER 7 DYNAMIC
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(a) (i) State the formula used for the calculation of work done.
__________________________________________________________
(ii) Calculate the work done.
(b) (i) State two units of power.
__________________________________________________________
(ii) By using the formula, Power = work( J) / time(s). Find out the power of the
man if he used 10 seconds to run up the stairs.
