His research that is what made him an influential and controversial psychologist<span />
Answer:
80m, assuming g=10m/s^2
Explanation:
40m/s will be reduced to 0m/s in 4 seconds. 4 seconds x 40m/s would be 160m up, but you will only get half of that because you decelerate linearly to 0m/s. This leaves you with 4 x 20 = 80m.