Exercises - Force and Motion 5

1. Which of the following properties of a solid object cannot be changed by a force?
  1. Length
  2. Mass
  3. Shape
  4. Speed

2. A box of mass 20kg is placed on a smooth horizontal surface. Find the acceleration of the box when a 120N force is acting on the box horizontally.
  1. 6 ms-2
  2. 5 ms-2
  3. 4 ms-2
  4. 7 ms-2

3. A net force of 30 N causes a block to accelerate at the rate of 6 m/s2. Determine the mass of the block.
  1. 5 kg
  2. 6 kg
  3. 7 kg
  4. 8 kg

4. A box of mass 5 kg moved with constant velocity when it was acted by a force of 15 N. Find the magnitude of the friction exert on the box.
  1. 50 N
  2. 15 N
  3. 35 N
  4. 65 N

5. The impulse exerts on an object can be increased by
  1. increasing the net force acting on the object.
  2. increasing the time of action of the force on the object.
  3. putting more mass on the object.

6. A 5N force is applied on an object for 10s. The object accelerates from 2ms-1 to 5 ms-1. Find the impulse exerts on the object.
Answer: 50

7. A billiard ball of mass 0.1 kg is stationary on a smooth billiard table. An impulse of 3.0 Ns is given to the ball horizontally. What is the velocity of the ball after the impact?
Answer: 30

8. A car of mass 1500kg was traveling at 50 m/s before it collided with a tree and stopped. If the time of collision was 0.05 seconds, find the magnitude of the impulsive force acted on the car during the accident.
Answer: 1500000

9. An astronaut found that his weight is lower on the surface of moon compare with on the surface of the earth. This is due to
  1. His mass decreases when he reaches at the moon.
  2. The gravitational field strength on the surface of the moon is lower than on the surface of the earth.
  3. There is no gravitational force on the surface of the moon.

10. The gravitational field strength on the Moon is about 6 times less than that on the earth. If the weight of a man is 820N on the earth, what will be his weight on the Moon?
  1. 137N
  2. 82N
  3. 4920N