A pole vaulter vaults over the bar and falls onto thick padding. He lands with a speed of 9.8m/s; the padding then brings him to a stop in a time of 0.40s. What is the average force on his body due to the padding during that time interval? Express your answer as a fraction or multiple of his weight.
[Hint: The force due to the padding is not the only force acting on the vaulter during the 0.40s interval.] (Answer in the textbook came up with: 3.5 times his weight) Trouble figuring out how they came up with that.