# physics

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For a ballistics study a 1.9 gram bullet is fired into soft wood at 380 meters/sec and penetrates 15 cm.

a.) find the retarding force (resistance) in N.

b.) the time needed to stop the bullet in sec.

c. acceleration of the bullet in meters/sec.

• physics -

a) initial kinetic energy = (force) x (penetration distance)
Solve for the force, F = .
Use kg and meters for doing the calculation.

b) Vaverage * time = (Vo/2)*time = 0.15 m
Solve for the stopping time.

Vo is the initial velocity, 380 m/s

c) a = F/m = Vo/(stopping time)
(You should get the same answer wither way)

• physics -

f=2.41N

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