# Force Problem

sheevz
Force Problem!

## Homework Statement

a ball of mass 2.0kg is dropped from a height of 10m. the speed of the ball is measured as 12.5m/s just before it hits the ground. what was the work done against air friction during this fall?

## The Attempt at a Solution

totally lost on where to begin can someone help me start? I am not finding anything on work itself as a force, is it a force?

konthelion
Work is not force. Exerting a force is not the same as doing work.

Work = force*distance.

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Homework Helper
So in this case, Work = mg * 10m. See what that comes out to first.

Then, using some basic equations of motion, you want to work out what the speed of the ball would have been, neglecting air resistance. Now, we know what the actual speed was, accounted for air resistance. Then use the formula for kinetic energy to get you to the end =]

physixguru
What is the work done against gravity my friend?

sheevz
so if work is mg*distance
then would the work be 2.0kg*10m= 20kgm?

arunbg
or 20J, now what is the actual kinetic energy of the ball at the bottom?