the force acts on a 50g ball varies with time.if the initial velocity of the particles is 20m/s.what is the average acceleration of ball during this time?

You would have to know the force to determine what the average acceleration is. Knowing the initial velocity does not help at all.

what acceleration is imported to a football when the player kicked it with a force of 25 N? mass of football 0.40kg

To find the average acceleration of the ball, we need to know the force acting on the ball as a function of time. However, the given information only includes the initial velocity of the ball. Without knowing the force acting on the ball, we cannot determine the average acceleration.

Acceleration is defined as the rate at which an object's velocity changes. Without additional information about the force acting on the ball, we cannot determine how its velocity changes over time, and therefore we cannot calculate the average acceleration.

If you have access to the force as a function of time or any other relevant information, please provide it so that we can help you calculate the average acceleration of the ball.