If action is always equal to the reaction, explain how a horse can pull a cart.
The horse pulls the cart with a force (action) in the forward direction. The cart also pulls the horse with an equal force (reaction) in the backward direction. This way, the two forces get balanced. The horse pushes the ground with its feet in the backward direction, while pulling the cart. So, the reaction of earth makes it move in the forward direction alongwith the cart.
In the following example, try to identify the number of times the velocity of ball changes:
“A football player kicks a football to another player of his team who kicks the football towards the goal. The goalkeeper of the opposite team collects the football and kicks it towards the player of his own team”.
Why do you fall in the forward direction when a moving bus brakes to a stop and fall backwards when it accelerates from rest?
When a moving bus brakes to a stop, the lower part of our body which is in contact with the bus comes to rest while the upper part of our body tends to keep moving due to inertia of motion. Hence, one tends to fall forward. When the bus accelerates from rest, the lower part of our body comes into motion alongwith the bus while the upper part of body tends to remain at rest due to inertia of rest. Therefore, we fall backwards.
Explain why some of the leaves may get detached from a tree if we vigorously shake its branch.
Initially, the tree and the leaves are in a state of rest. When the branches are shaken vigorously, they come into motion while, the leaves tend to remain in a state of rest due to inertia of rest. Therefore, the leaves get detached from the branches and fall down.
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