7. 80-g bullet moving at 480 m/s penetrates a tree trunk to a depth of 4. 5 cm.

Question

7. 80-g bullet moving at 480 m/s penetrates a tree trunk to a depth of 4. 5 cm. Use work and energy considerations to find the average frictional force that stops the bullet. Your response differs from the correct answer by more than 10%. Double check your calculations. N Assuming the friction force is constant, determine how much time elapses between the moment the bullet enters the tree and the moment it stops moving. Your response differs from the correct answer by more than 10%. Double check your calculations.

Explanation / Answer

by work energy theorem,

1/2* 7.80*10^-3 *480^2 = Friction force *0.045

Friction force = 19968 N

b.) s = ut +1/2*a*t^2

0.045 = 480*t + 0.5*a*t^2 where a = 19968/0.0078 = 2560000 m/s2

t = 7.766 *10^-5 sec

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