When jumping straight down, you can be seriously injured if you land stiff-legged. One way to avoid injury is to bend your knees upon landing to reduce the force of the impact. A 77.5 kg man just before contact with the ground has a speed of 6.22 m/s. In a stiff-legged landing he comes to a halt in 2.08 ms. Calculate the average net force that acts on him during this time.