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## Homework Statement

Say we've got a stationary brick wall, and a blob of jello with mass m is launched at the wall with speed v. The blob has length d along the direction of motion.

The blob splatters onto the wall when it hits. How much average force will the wall feel?

## Homework Equations

The work done to stop the blob must be the same as the energy that was in the blob while it was moving, so:

F d = E

Also, from the second law, F = m Δv / Δt

## The Attempt at a Solution

Solving that first equation gives:

F = E / d = 1/2 mv² / d

On the other hand, if I had used the second equation, I would get:

F = mv / Δt = mv / (d / v) = mv² / d

So, doing it this way, I calculate twice as much force. What gives? Where did I go wrong?