Saved Bookmarks
| 1. |
One gets less hurt when one jumps from a height on sand than on hand floor. Why ? |
|
Answer» Solution :When a man jumps on any surface, the surface in contact with the man gets a LITTLE depressed. This depression is more in the case of a sandy surface than of a hand floor. The initial potential energy of the man is the same in both cases. So the kinetic energy just before HITTING the ground is also the same. Suppose , the mass of the man = m and he jumps from a height h. The average reaction force of the ground on him is R. He stops after depressing the ground by x. so his kinetic energy is used up in WORK done against the NET reaction force R-mg. As kinetic energy just before hitting the ground = potential energy at height = h =mgh , `(R -mg )x =mghor, R =(1+ h/x) mg` As x is more for a sandy surface , R is less and hence, the man is less hurt. |
|