Worksheet #1
Physics for grade 9
I. Write true for the correct statement or false for the wrong statement.
1. For an object which is lifted up ward, work done by gravity is positive.
2. In the absence of external force momentum is conserved in any type of collision
3. During elastic collision total kinetic energy before collision is less than total kinetic energy
After collision.
4. The inertia of an object depends on its mass.
5. Momentum takes the direction of velocity.
6. Friction always tends to act in the direction opposing motion.
II. Match the column “A” with the similar concepts under column “B”
“A”
11. Dynamic friction
A.
“B”
Unit less
Linear momentum
B.
Limiting friction
13. Impulse
C.
Change in momentum
14. Maximum value of static friction
D.
Mass x velocity
15. Coefficient of friction
E.
Kinetic friction
F.
Static friction
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III. Among the given alternative choose the best answer
16. The unit of work may be expressed by _____________
A. N.m
2
B. kg. m
s2
B. J
D. All of the above
17. A force does a negative work when _____
A. The force is opposite to the displacement
B. The force is perpendicular to the displacement
C. Both the displacement and force are positive
D. Both the displacement and force are negative
18. An object of mass m moving with velocity across a level surface comes to rest after traveling a
distance d. what is the work done by friction?
A. - Mvd
B.
1
mv2
2
C.
1
1 2
mr d
2
D. Zero
19. In raising an object to a given height ‘h’ by means of inclined plane, as compared with raising the
object vertically to the same height h, there is a reduction in
A. Force required
B. Work required
C. Mechanical advantage
D. distance pushed
20. A body having a mass m and kinetic energy KE. What is the momentum of the body?
A.
KE
B.
2m
2KE M
2KE
m
C.
D.
2m
KE
21. Calculate the power developed by an athlete weighting 800N, When he runs up a staircase, climbing
20m in 4 seconds.
A. 4 x 103 Watt
B. 16 x 103Wat
C. 10Watt
D. 30Watt
22. A train is traveling at 20 m s along a straight level road. Its engine have a power out put of
800,000watt Find the force acting on the train?
A. 40,000N
B. 1600,000N
C. 30,000N
D. 70,000
23. In an elastic collision
A. Momentum is not conserved.
B. The kinetic energy before collision is greater than kinetic energy after collision
C. Kinetic energy is conserved
D. The kinetic energy before collision is less than kinetic energy after collision
24. If the velocity of an object is doubled, its kinetic energy is __________.
A. Halved
B. doubled
C. quadrupled
D. remain the same
25. Newton’s pairs of forces
A. Are equal in magnitude
B. Are opposite in direction
C. Lie on the same line of action
D. All are correct answers
26. A car of mass 4000kg is moving at 20m/s due south along a straight road. What is its linear
momentum?
A. 8 x104 kg m/s North
C. 8 x 104 kg m/s South
B. 8 x104 kg m/s East
D. 8 x 104 kg m/s west
27. A bird flies by pushing air downwards. The air in turn pushes the bird upwards. Which of the
The physics laws does the bird uses of fly?
A. Law of conservation of energy
2
B. Law of gravity
C. Newton’s third law
D. Newton’s 1st law
28. An object of mass m moves with constant speed on a horizontal rough surface by the action
of horizontal force of magnitude F. If the coefficient of kinetic friction is µk
What is the magnitude of the acceleration when the force is removed?
A. g
B.
k g
C. µkg
2
D. 0
29. If an object is resting on an inclined plane
A. The normal contact force is increased
B. Frictional force is increased
C. Weight increases
D. there is component of the weight along the inclined plane
30. A block slides down a 370 frictionless inclined plane starting from rest at the top. Just up on reaching
the bottom its velocity is 12m/s. What is the length of the inclined plane? (Sin370 =0.6 cos370 = 0.8,
= 10m/s2 ) ( use law conservation of energy concept )
A. 12m
B. 24m
C. 6m
d. 10m
31. A 2kg body is moving to the right with a velocity of 15m/s. It collides with a 1kg body which was at
rest at the origin. After collision they stick together. Their velocity after collision is
A. 5m/s
B. 15m/s
C. 10m/s
D. 3m/s
32. The loss of kinetic energy after collision in the preceding question is
A. 225J
B. 37.5J
C. 187.5J
33. In a closed system
A. The total linear momentum will remain constant
B. The total energy will remain constant
C. The change in total linear momentum is zero
D. All
34. A body is said to be under translational equilibrium.
A. If it is at rest
B. If it is moving with constant velocity
C. If the vector sum of all forces acting on it is equal to zero
D. All
35. Which of the following is a contact force?
3
D. 150J
A. Gravitational force
C. electric force
B. Magnetic force
D. gravitational force
36. An object of mass 40kg is found at a height of 10m, above the ground surface. What is the
gravitational potential energy (take g = 9.8 m/s2)
A. 3920J
B. 2860J
C. 9800J
D. 4200J
37. A particle of mass m = 30gm, attached to a spring of force constant k = 200N/M is oscillating along
the x – axis about the equilibrium position x = 0 as shown in fig below
If the amplitude xmax = 10cm, what is the kinetic energy of the particle when it reaches the
equilibrium position?
A. 1000J
B. 100J
C. 1J
D. 10J
38. A ball is thrown straight up. It rises for a while and drops back to the ground. Which of the
following energy transformation best describe the process?
A. Chemical
B. Kinetic
C. Potential
D. Kinetic
kinetic
potential
chemical
potential
kinetic
potential
potential
kinetic
IV. Fill the blank spaces
39. ____________ is the frictional force between two objects that are trying to move against each
other
but are not yet moving.
40. ____________ is the rate of doing work.
41. The SI unit of force is ____________
42. In elastic collision both _______________ and ___________ are conserved.
V. Work out (Use the space at the back of your answer sheet for your answer)
43. If a ball of mass m is released from point ‘A’ which is 80cm find the speed the ball at point B
44. Two balls of mass 1kg and 2kg moving towards each other with a speed of 2 m s and 6 m s
4
respectively collide each other.
A. Find the velocity of each ball if the collision is perfectly inelastic
B. Find the kinetic energy drop
45. A 1000kg car accelerates uniformly from 10m/s to 30m/s in 2seconds Find
a. The change in momentum in this time
b. Impulse
c. Change in kinetic energy
d. Work done
e. Average power
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