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**1. The problem statement, all variables and given/known data**

the question goes like this

a man of mass 70kg falls onto a rescue cushion from a height of 7 m he comes to rest 0.2s after he reaches the cushion the cushion is 2m high when inflated

a)find the impact force acting on him (take the weight of the man into account)

b)by how many times is the impact force greater than his weight?

**2. Relevant equations**

**3. The attempt at a solution**

a) For a, I first calculated the change of momentum of the man, which is 700kgms-1, then the impact force will be the change of momentum over time, which gives an answer of 3500N, which is a wrong answers since the answer in the book is 4200, I don't get it...