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## Homework Statement

Kwaku Boateng is a former Canadian Olympic high jumper. If an average vertical ground reaction force of 1959.6 N acted on Kwaku's foot for 0.20 s during the upward phase of his jump, and Boateng's mass is 79.1 kg, what would his take-off velocity be?

## Homework Equations

ΣFΔt=mΔv

## The Attempt at a Solution

I tried it twice...

Attempt 1:

ΣFΔt=mΔv

Δv=(ΣFΔt)/m

Δv=(1959.6)(0.20)/79.1

Δv=4.95m/s

The online assignment says that this answer is incorrect.

Attempt 2:

ΣFΔt=mΔv

V

_{f}-V

_{i}=(ΣFΔt)/m

V

_{i}=-[(ΣFΔt)/m]+V

_{f}

V

_{i}=(1959.6)(0.20)/79.1

V

_{i}=-4.95m/s

The online assignment says that this answer is incorrect.

Should I be using another equation? Or have I made a simple mistake?

Thank you in advance for your help!