# Momentum average force

## Homework Statement

A 6 kg steel ball strikes a wall with a speed of 11.2 m/s at an angle of 50.5 degrees with the normal to the wall. It bounces off with the same speed and angle. If the ball is in contact with the wall for .219s, what is the magnitude of the avg force exerted on the ball by the wall. Answer in units of N.

## Homework Equations

change in momentum (delta p)= avg force * change in time

In this case, because there is no change in momentum, wouldnt that mean the avg force would be zero?

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alphysicist
Homework Helper

## Homework Statement

A 6 kg steel ball strikes a wall with a speed of 11.2 m/s at an angle of 50.5 degrees with the normal to the wall. It bounces off with the same speed and angle. If the ball is in contact with the wall for .219s, what is the magnitude of the avg force exerted on the ball by the wall. Answer in units of N.

## Homework Equations

change in momentum (delta p)= avg force * change in time

In this case, because there is no change in momentum, wouldnt that mean the avg force would be zero?
There is a change in momentum. Remember that momentum is a vector and even if it only changes direction, that still means that momentum is not conserved, and so there is an external force causing that change.

i thought momentum was ALWAYS conserved....??

fluidistic
Gold Member
i thought momentum was ALWAYS conserved....??
Not if there is an external force acting upon the system you are considering. If you consider the ball as being your system, then the bat will create an external force...