Class Notes NCERT Solutions for CBSE Students
Question: A man stands behind a trolley, will it move?
Answer: No, the trolley will not move, when a man stands behind the trolley. The trolley will only move, when the man will make an interaction with the trolley and push it. For every force to come in action interaction with other object is necessary.
Question: What happens when two people push an object from same direction?
Answer: When two people push or pull something together in same direction, the force applied by them get added and the action becomes easy.
Question: How can force change the state of motion?
Answer: Force can change the state of motion by changing the direction of the motion and by changing the speed of the motion. Force in the direction of the motion increase the speed and force in opposite direction decrease the speed.
Question: What is the state of the motion?
Answer: State of motion of an object is its speed and its direction. State of zero motion means state of rest. An object can be in two positions one at rest or at motion. Any changes in this position can be the change in the state of motion.
Question: What effect can force have on the shape of the object?
Answer: Force can changes the shape of the object. When some force is applied on any object some change in the shape of the object definitely takes place. Sometimes this changes in the shape of the object definitely takes place. Sometimes this changes is so small that it is not visible, but change always takes place.
Question: What do you understand by contact force?
Answer: Contact force means the force which comes in action only when two objects comes in contact with each other. Different forces like muscular force, friction etc, are the contact force.
Question: What is muscular force? Why is it a contact force?
Answer: The force exerted by the action of the muscles is called muscular force. Muscular activities like running, bending, walking etc. produce muscular force. Muscular force is a contact with an object.
