THE UNITED REPUBLIC OF TANZANIA

PHYSICS FOUNDATION EXAMINATION

UNDERSTANDING FRICTION EXAMINATION

FORM THREE
031 PHYSICS
TIME 3; 00hrs January 2024.

Instructions
1. This paper consists of sections A, B and C with a total of elven (11) questions
2. Answer all questions in section A and B and only two (2) questions from section C
3. Non-programmable calculators and mathematical tables may be used
SECTION A (16marks)
Answer all questions in this section
1. For the each items (i) – (x), choose the correct answer from among the given alternatives and
write its letter besides the item number in the answer booklet provided (10marks)
(i) A boy rolls a rubber ball on a wooden surface. The ball travels a short distance before coming to
rest To make the same ball travel longer distance before coming to rest , he may
A. Spread a carpet on the wooden surface
B. Cover the ball with piece of cloth
C. Sprinkle talcum powder on the wooden surface
D. Increase energy of rolling
(ii) Which of the following relation is true regarding magnitude of friction?
A. Sliding friction > rolling friction > static friction
B. Static friction > sliding friction > rolling friction
C. Static friction > sliding friction = rolling friction
D. Static friction = rolling friction = dynamic friction
(iii) We slip while walking on a path having pond scum or green algae because:
A. The inertia of the motion
B. The friction is zero
C. The friction between the feet and the path is increased
D. The friction between the feet and the path is reduced
(iv) Which of the following is a wrong example of friction
A. Washing machine pushed along a floor
B. Sled sliding across snow
C. A person sliding down a slide
D. A person lifting a heavy object
(v) A block of mass 10kg is lying at the front desk of a classroom. The coefficient of static friction is
0.5. A force of 40N is applied to the book. The book will

F
fs

A. Move
B. Not move
C. Move up and down
D. Be thrown away
(vi) Which of the following statement(s ) is/are correct?
Statement1: bicycle tyres wear out due to high muscular force
Statement2: treads in tyres are made to increase the increase the grip with the surface
A. Only statement 1 is correct
B. Only statement 2 is correct
C. Both statements are correct
D. Both statements are incorrect
(vii) Which of the following statements is correct?
A. Friction act in the same direction as motion
B. Air friction can cause a body to become hot
C. A certain lubricant can reduce friction to zero
D. For a given body the frictional force depends on the area in contact with the surface.
E. Walking would be made is easier if friction did not exist
(viii) If the normal force is doubled , the coefficient of friction is
A. not changed
B. halved
C. doubled
D. tippled

(ix) Whenever the surfaces in contact tend to move or move with respect to each other , the force of
friction comes into play
A. Only if objects are solid
B. Only if one of the two objects is liquid
C. Only if one of the two objects is gaseous
D. Irrespective of whether the objects are solid, liquid or gaseous
(x) Friction is
A. Foe
B. Friend
C. Both (a) and (b)
D. None of these
2. Match the items in list A with the responses in list B by writing the letters of correct response in the
item number (6marks)
List A List B
i. Soapy floor A. Shape of the body that reduces
ii. Streamlined friction
iii. Viscosity B. Less friction
iv. Lubricant C. Coefficient of static friction in
v. Limiting friction inclined plane
vi. 𝜇 = tan𝜃 D. Coefficient of dynamic friction in
an inclined plane
E. Friction force between layer of the
fluid
F. Oil and grease
G. Maximum possible value of static
friction
H. Maximum possible value of
dynamic friction

SECTION B (54marks)
Answer all questions from this section
3. (a) Explain briefly why people are able to walk and hold objects. (02marks)
(b) Explain why most vehicles have their engines directly over the drive wheels.(02marks)
(c) A 50g mass is placed on a straight track slopping at an angle of 450to the horizontal as shown in
figure .calculate
i. The acceleration of the load as it slides down the slope (2.5marks)
ii. The distance moved in 0.2seconds (2.5marks)
R
50g

F
𝜃 mg

4. (a) Why friction is said to be enemy to human being? Give three points (3marks)
(b) Friction some time is good and some time is bad. When it looks to be bad can be minimized to
some extent. What can you do to solve this problem of friction when it looks to be bad? Give
three points (3marks)
(c) A block of mass 270kg is pulled along a horizontal surface .If the coefficient of kinetic friction
between the block and the surface is 0.4, what is the force acting on the block as it slides?
(3marks)

5. (a) What is Rolling friction? Give two example (2marks)

(ii) When the body is moving at an inclined plane, name the forces acting on the body .Include
their formula. (03marks)
6. (a) Explain why the coefficient of static friction is larger than the coefficient of kinetic friction?
(02.5marks)
(b) A marble is released on a 300 inclined plane. Once at the foot of the plane it moves in turn on three
different horizontal surface that are covered with
a) Silk cloth
b) A layer of sand
c) A glass sheet
On which surface will the marble move the shortest distance. Give reason for your answer
(02.5marks)
(c) A 42kg refrigerator is placed on the back of stationary pick –up as shown in figure below. The
coefficient of static friction between the refrigerator and the pick – up bed is 0.44. At what rate the
pick-up can accelerates without the refrigerator sliding off back? (04marks)

7. (a) Show that coefficient of static friction of a body moving at constant speed or when the body
is at rest for an inclined plane at angle 𝜃 with horizontal is given by μs = tan 𝜃(3marks)
(b) When the body begins to slide show how you can get acceleration under the following
condition
(i) When the coefficient of friction is not equal to zero (3marks)
(ii) When the coefficient of friction is zero (3marks)

8. (a) Truck A and truck B having a maximum carrying capacity of 1tone each, were loaded with 300kg
and 600kg of maize each respectively. After a 3000km drive, truck B tyres were worn out than truck
A tyres .Explain why truck B tyres were more worn out than A if both trucks had new tyres from the
same company? (4marks)
(b) Take time and observe the figure below. fr
M

600
From the figure a block of mass M slides down a plane inclined at an angle of 600 to the
horizontal with an acceleration equal to half of acceleration due to gravity. Show that the
coefficient of kinetic friction μk = √3 – 1. (5marks)
 SECTION C (30 marks)
Answer two (2) questions from this section
9. (a) Give three examples of static friction(3marks)
(b) (i) State any three laws of friction? (3marks)
(ii) Two boys one riding their bikes on the same concrete road .One students bike had new tyres
whereas the other had used tyres.Which of them is mostly likely to skid while moving through a road
which has lubricant oil spilled over it? Explain your answer. (4marks)
(c) A horizontal force of 15N is applied to a 5kg box placed on a horizontal table .Will the box move
if the coefficient of friction is 0.4? Show calculation finally leave the comment. (5marks)

10. A rectangular box of mass 10kg rests on an inclined plane. Let the coefficient of static friction be
0.55 and that of kinetic friction be 0.2s
(a) At what angle will the box begins to slide? (8marks)
(b) If the incline is kept at that angle after the box begins to slide, what will be the box’s
acceleration? (7marks)
11. (a) Why friction is likely to arise? (06marks)
(b) In the first day of the beginning of new year 2024, the rain rained at Kalemela A village which
found in Urambo Tabora .The road become wet and the coefficient of kinetic friction between
road and tyres was 0.1.Two similar cars ,A and B , are travelling at speed of 15m/s and 30m/s
respectively. Brakes are suddenly applied to each of the cars. How far will each of the cars travel
before coming to stop? (9marks)

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