Conceptual Questions Based on Laws of Motion

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Conceptual Questions Based on Laws of Motion

Q.1. Can a single isolated force exist in nature? Explain your answer.

Answer: No, a single isolated force cannot exist in nature because it violates the Newton’s third law.

Q.2. Why it is not possible to push a car from inside?

Answer:

(i) When you push a car from inside, the reaction force of your pushing is balanced out by your body moving backward.

(ii) The seat behind you pushes against to bring things to static equilibrium.

Q.3. When walking on ice one should take short steps. Why?

Answer: It is to avoid slipping. Smaller step causes more normal force and thereby more friction.

Q.4. Can we predict the direction of motion of a body from the direction of force on it?

Answer In free body diagrams, the force of friction is always parallel to the surface of contact. The force of kinetic friction is always opposite the direction of motion.

Q.5. There is a limit beyond which the polishing of a surface increases frictional resistance rather than decreasing it why?

Answer:

(i) Due to excessive polishing, more molecules of the two surfaces come closer. Thus they form more bonds and offer great resistances.

(ii) Because friction arises due to molecular adhesion i.e. due to electrostatic forces.

Q.6. Why does a parachute descend slowly?

Answer: A parachute is a device used to slow down on object that is falling towards the ground. When the parachute opens, the air resistance increases. So the person can land safely.

Q.7. The momentum of a system of particles is always conserved. True or false?

Answer: True. The momentum of a system of particles is always conserved.

Q.8. When a person walks on a surface, the frictional force exerted by the surface on the person is opposite to the direction of motion. True or false?

Answer: False. The frictional force exerted by the surface is not opposite to the direction of motion.

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