A 7.80-g bullet moving at 690 m/s penetrates a tree trunk to a depthof 6.5 cm. (

Question

A 7.80-g bullet moving at 690 m/s penetrates a tree trunk to a depthof 6.5 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 how muchtime elapses between the moment the bullet enters the tree and themoment it stops moving.

(a) Use work and energy considerations to find the averagefrictional force that stops the bullet.
N

(b) Assuming the friction force is constant, determine how muchtime elapses between the moment the bullet enters the tree and themoment it stops moving.

Explanation / Answer

work done = 0.5m(v22-v12), v2=0, v1=690m/s frictional force * distance = -0.5 (7.8/1000)(690)2 frictional force = -1856.79Nm / (6.5/100)m frictional force = -28566 N negative sign indicates that it is to the different directionof bullet F=ma, a= F/m = -28566/.0078 = -3662307.69 m/s2 v=u+at, while v= finial velocity and u = initialvelocity 0=690 - 3662307.69 t t= 1.884 x10-4s not sure if this is correct hope it helps v=u+at, while v= finial velocity and u = initialvelocity 0=690 - 3662307.69 t t= 1.884 x10-4s not sure if this is correct hope it helps

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