1. The problem statement, all variables and given/known data 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? 2. Relevant equations ΣFΔt=mΔv 3. 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 Vf-Vi=(ΣFΔt)/m Vi=-[(ΣFΔt)/m]+Vf Vi=(1959.6)(0.20)/79.1 Vi=-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!