In the following example, try to identify the number of times the velocity of the 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 a player of his own team?
Also identify the agent supplying the force in each case.
We need to apply first law of motion and identify what force is applied which changes the velocity (state i.e. rest, direction, motion) of the ball. A force when applied can produce acceleration in body.
| Event | Agent | force and Action |
|---|---|---|
| A football player kicks a football | football player | push force, ball moves from rest. |
| to another player of his team who kicks the football towards the goal. |
another player | force, changes direction of ball. |
| The goalkeeper of the opposite team collects the football |
goal keeper | force to stop ball (ball velocity is zero now) |
| and kicks it towards a player of his own team |
goalkeeper | force moves ball from rest to motion in opposite direction. |
While driving on a highway, an insect strikes on the car windshield and splatters. Which experiences greater impact (force): an insect or the windshield?
An object of mass 1 kg travelling in a straight line with a velocity of 10 m/s collides with, and sticks to, a stationary wooden block of mass 5 kg. Then they both move off together in the
same straight line. Calculate the total momentum just before the impact and just after the impact. Also, calculate the velocity of the combined object.
It is difficult to balance our body when we accidentally slip on a peel of banana. Explain why?
A man pushes a box of mass 50 kg with a force of 80 N. What will be the acceleration of the box due to this force? What would be the acceleration if the mass were doubled ?
A TV set is lying on a table. The TV set experiences a gravitational force (pull) downwards (FW) by the Earth. It also experiences a force on it due to table in contact i.e. (FTable-TV) in upward direction. Do these forces form an action-reaction pair? Do these forces follow Newton's third Law of motion?
A hammer of mass 500 g, moving at 50 m/s, strikes a nail. The nail stops the hammer in a very short time of 0.01 s. What is the force of the nail on the hammer ?
From a rifle of mass 4 kg, a bullet of mass 50 g is fired with an initial velocity of 35 m/s. Calculate the initial recoil velocity of the rifle.
A hockey ball of mass 200 g travelling at 10 m s-1 is struck by a hockey stick so as to return it along its original path with a velocity at 5 m s-1. Calculate the change of momentum occurred in the motion of the hockey ball by the force applied by the hockey stick.
A bullet of mass 10 g travelling horizontally with a velocity of 150 m/s strikes a stationary wooden block and comes to rest in 0.03 s. Calculate the distance of penetration of the bullet into the block. Also calculate the magnitude of the force exerted by the wooden block on the bullet.
In the following example, try to identify the number of times the velocity of the 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 a player of his own team?
Also identify the agent supplying the force in each case.
Why is it easier to stop a tennis ball in comparison to a cricket ball moving with the same speed ?
An object experiences a net zero external unbalanced force. Is it possible for the object to be travelling with a non-zero velocity? If yes, state the conditions that must be placed on the magnitude and direction of the velocity. If no, provide a reason.
While catching a fast moving ball, fielder gradually pulls his hand backwards. Give reasons.
When two objects act on each other, does action-reaction force pair cancel out each other?