Conservation of Energy

The Undergraduate (3/3)

(part 1) A footloose undergraduate weighing 70 kg wants to bobsled down the Louvre. He pays the French government several million dollars in collateral, then sits on a bobsled on the top on of the Louvre. Then, he pushes himself off with a speed of 5 m/s. Assume the undergrad is 21 m above the ground and that g = 9.8 m/s.

(part 2) Luckily for our undergraduate, he is not going at more than 40 mph, because there is this thing called "friction". Assume our daredevil rider loses 7070 J of energy whilst riding.

To make sure he doesn't accidentally kill himself, he has set up a landing pad, which turns out to be a vertical mattress that you can just treat as a spring with $k$ = 50,000 N/m. What distance he travel before stopping, from when he first touches the mattress (assume friction is negligible on the ground, but there was friction on the Louvre). Round your answer to the nearest hundredth. Express your answer in m.