As shown in the figure below, a bullet is fired at and passes through a piece of
ID: 2143250 • Letter: A
Question
As shown in the figure below, a bullet is fired at and passes through a piece of target paper suspended by a massless string. The bullet has a mass m, a speed v before the collision with the target, and a speed
after passing through the target. The collision is inelastic and during the collision, the amount of energy lost is equal to a fraction
of the kinetic energy of the bullet before the collision. Determine the mass M of the target and the speed V of the target the instant after the collision in terms of the mass m of the bullet and speed v of the bullet before the collision. (Express your answers to at least 3 decimals.)
Explanation / Answer
energy lost =mv^2/2 - m ( 0.546v)^2 /2 - MV^2/2
that is equal to 0.293 K.E. bBc = 0.293mv^2 /2
mv^2/2 - m ( 0.546v)^2 /2 - MV^2/2 = 0.293mv^2 /2
MV^2 =0.161mv^2 ---- i
and momentum conservation,
mv +0 = MV + m x 0.546v
MV = 0.454mv ------ ii
i / ii
V = 0.161mv^2 / 0.454mv = 0.355v m/s
b) M = 0.454mv / 0.355v = 1.28m
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