Why friction doesn’t roll a ball backward if no force is pushing or pulling it?
Q.1. Why friction doesn’t roll a ball backward if no force is pushing or pulling it?
Ans. Friction comes into action only in presence of an applied force.
Q.2. What is the force required to accelerate a 2 kg mass by 5 m s-2?
Ans. F= 2 x 5 = 10 N
Q.3. If a man jumps out from a boat to the bank of the river, the boat moves backwards. Identify the action and reaction in this situation.
Ans. The push of the man on the boat is action. The boat exerts an equal force on the man is reaction.
Q.4. Kicking a football requires less force than kicking a basketball. Why?
Ans. Inertia of an object is measured by its mass. As mass of basketball is more, hence more effort.
Q.5. When a carpet is beaten with a stick it releases dust. Explain why?
Ans. The dust particles lying on the carpet possess inertia of rest, When the carpet is beaten, dust particles resist the change in state and fall down.
Q.6. How does the safety belt in the car help when a moving car applies brake suddenly ?
Ans. With the application of brakes, car slows down but due to inertia body continues to be in same state of motion. Safety belts exert a force on body to slow down its forward motion.
Q.7. Name the physical quantity that measures inertia. State its SI unit.
Ans. Mass. Its SI unit is kilogram (kg).
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