A 7.80-g bullet moving at 570 m/spenetrates a tree trunk to a depth of 5.9 cm. (

Question

A 7.80-g bullet moving at 570 m/spenetrates a tree trunk to a depth of 5.9 cm. (a) Use work and energy considerations to find the averagefrictional force that stops the bullet.      _____N (b) Assuming the friction force is constant, determine howmuch time elapses between the moment the bullet enters the tree andthe moment it stops moving.
A 7.80-g bullet moving at 570 m/spenetrates a tree trunk to a depth of 5.9 cm. (a) Use work and energy considerations to find the averagefrictional force that stops the bullet.      _____N (b) Assuming the friction force is constant, determine howmuch time elapses between the moment the bullet enters the tree andthe moment it stops moving.

Explanation / Answer

mass m = 7.8 g = 7.8 * 10 -3 kg speed v = 570 m / s kinetic energy K = ( 1/ 2) m v 2                          =2534.22 J From work energy theprem, work done = change in K.E average frictional force * displacement = 2534.22J from this frictional force = 2534.22 / 5.9 cm                                    = 2534.22 / 0.059 m                                    = 42952.88 N (b). Accleration a = -F / m initial velocity u = 570 m / s final velocity v = 0 m / s So, required time t = ( v - u ) /a substitue values wegetanswer                          

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