Question

I assume you came across a dark canyon. Wondering how deep it was, you remembered this lab. You drop a rock into the canyon and time the fall. 2.0 seconds later, you hear it hit the bottom. Can you jump in safely? show your reasoning.

Answer 1

Depth of the canyon = 0.5gt^2 = 0.5*9.8*2^2 = 19.6 m

velocity at the bottom when his beet touches the floor first , u = sqrt(2gh) = sqrt(2*9.8*19.6) = 19.6 m/s

Lets the height of the person be 1.8m. After his feet touches the floor of the canyon he bends his legs, so maxim displacement of center of mass during impact will be 0.9 m.

acceleration during impact , a = u^2/2s = 19.6^2/(2*0.9) = 213 m/s^2

A body can withstand maximum 5g of force (acceleration).

This (213 m/s^2) is more than 5g which is 5*9.8 = 49 m/s^2

So, he can not jump safely.

  

answered by: anonymous