# LET Reviewer - PHYSICAL SCIENCE (MECHANICS) Set 2

Majorship LET Reviewer LET Reviewer for Physical Science
PRACTICE TEST IN PHYSICAL SCIENCE (MECHANICS)

1. According to Newton’s second law of motion
a. force on an object is equal to its acceleration divided by its mass
b. force on an object is equal to the product of its mass and acceleration
c. mass of an object is equal to the product of the force on it and its acceleration
d. acceleration of an object is equal to the product of the force on its and its mass

2. The acceleration produced by a net force on an object is
a. directly proportional to the mass
b. inversely proportional to the net force
c. in the same direction as the net force
d. all of the above

3. The weight of an object of an object
a. refers to its inertia
b. is the quantity of matter it contains
c. is the force with which it is attracted to the earth
d. is basically the same quantity as its mass but expressed in different units

4. The force that accelerates a rocket into outer space is exerted on the rocket by the exhaust gases. Which Newton’s law of motion is illustrated in this situation?
a. First law of motion
b. Second law of motion
c. Third law of motion
d. cannot be determined

5. An object weighs 30 N on earth. A second object weighs 30 N on the moon. Which object has the greater mass?
a. the one on earth
b. the one on the moon
c. they have the same mass

6. As an airplane climbs,
a. its mass increases
b. its mass decreases
c. its weight increases
d. its weight decrease

7. Suppose a cart is being moved by a force. If suddenly a load is dumped into the cart so that the cart’s mass doubles, what happens to the cart’s acceleration?
a. it doubles
b. it triples
c. it halves
d. it stays the same

8. A player hits a ball with a bat. The action force is the impact of the bat against the ball. What is the reaction to this force?
a. the weight of the ball
b. the air resistance on the ball
c. the force of the ball against the bat
d. the grip of the player’s hand against the bat

9. When a football is kicked, the action – and – reaction forces do not cancel each other because
a. they are not truly equal and opposite
b. they are not acting at the same time
c. they are acting on two different bodies
d. all of them

10. A car accelerates along a road. Viewed from outside the car, what is the force that accelerates it?
a. the engines pulling it forward
b. air rushing in behind the car as it moves
c. the wheels pulling forward on the wheels
d. the reaction force to the wheels pushing the road backward

11. A car travels in a circle with constant speed. The net force on the car is
a. directed toward the center of the curve
b. zero because the car is not accelerating
c. directed forward, in the direction of travel
d. none of them

12. Suppose the force of friction on a sliding object is 10 N. The force needed to maintain constant velocity is
a. less than 10 N
b. more than 10 N
c. 10 N
d. 0 N

13. An apple weighs 1 N. The net force on the apple when it is at rest on top of your head is
a. 0 N
b. 0.1 N
c. 1 N
d. 10 N

14. An apple weighs 1 N. The net force on the apple when it is in free fall is
a. 0 N
b. 0.1 N
c. 1 N
d. 10 N

15. An unfortunate bug splatters against the windshield of a moving car. Compared to the force on the bug, the force on the car is
a. greater
b. smaller
c. the same

16. An unfortunate bug splatters against the windshield of a moving car. Compared to the acceleration of the bug, the acceleration of the car is
a. greater
b. smaller
c. the same

17. Two figure skaters who push off each other will move at the same speed if
a. they push with the same force
b. the ice does not cause any friction
c. there is no air resistance
d. they have the same mass

18. When two equal forces act on the same object in opposite directions, the net force is
a. smaller than either force
b. equal to each of the forces
c. zero
d. greater than either force

19. A tennis ball and a solid steel ball of the same size are dropped at the same time. Which ball has the greater force acting on it?
a. the tennis ball
b. the steel ball
c. the same force is acting on them

20. A tennis ball and a solid steel ball of the same size are dropped at the same time. Which ball has the greater acceleration? (assuming that the air resistance is negligible)
a. the tennis ball
b. the steel ball
c. they have the same acceleration

21. A ball rolling across the floor slows to a stop because
a. the forces are balanced
b. the net force equals zero
c. there is a net external force acting on it
d. the force that started it moving wears out

22. The momentum of an object is defined as the object’s
a. mass times its velocity
b. mass times its acceleration
c. force times its acceleration
d. force times the time interval

23. The momentum change of an object is equal to the
a. force acting on it
b. impulse acting on it
c. velocity change of the object
d. force acting on its times its velocity

24. Momentum of a system is conserved only when
a. the system is not moving
b. there are no forces acting on the system
c. there is no net external force acting on the system
d. there are no internal forces acting on the system

25. When the velocity of a moving object is doubled
a. its momentum is doubled
b. its acceleration is doubled
c. its kinetic energy is doubled
d. its potential energy is doubled

26. A rifle recoils from firing a bullet. The speed of the rifle’s recoil is small because the
a. momentum is conserved
b. rifle is more massive than the bullet
c. force against the rifle is relatively small
d. impulse on the rifle is less than the impulse on the bullet

27. In physics, work is done
a. in pushing against the wall
b. in preparing school lessons
c. in supporting an object on your shoulder
d. in lifting an object from the floor to the table

28. An object at rest may have
a. velocity
b. momentum
c. kinetic energy
d. potential energy

29. An object in motion need not have
a. velocity
b. momentum
c. kinetic energy
d. potential energy

30. What never changes when two or more objects collide in the absence of a net external force is
a. the momentum of each one
b. the kinetic energy of each one
c. the total momentum of all objects
d. the total kinetic energy of all objects

31. The amount of potential energy possessed by an elevated object is equal to
a. the distance it is lifted
b. the force needed to lift it
c. the power used to lift it
d. the work done in lifting it

32. A freight train rolls along a track with considerable momentum. If it were to roll at the same speed but had twice as much mass, its momentum would be
a. zero
b. doubled
d. unchanged

33. A job is done slowly and an identical job is done quickly. Both jobs require the same amount of work but different amounts of
a. energy
b. power
c. both energy and power
d. none of them

34. Which of the following statements is true about an object thrown upward under the influence of the earth’s gravity alone?
a. kinetic energy increases – potential energy increases
b. kinetic energy decreases – potential energy increases
c. kinetic energy increases – potential energy decreases
d. kinetic energy decreases – potential energy decreases

35. Which of the following statements is true regarding simple machines being used with the presence of friction?
a. work input is always greater than work output
b. work input is always smaller than work output
c. work input is always equal to the work output
d. cannot be determined