Question

A bullet of mass 0.012 kg and horizontal speed 70 m/s strikes a block of wood of mass 0.4 kg and instantly comes to rest with respect to the block. The block is suspended from the ceiling by a wire. Calculate the height to which the block rises. Also estimate the amount of heat produced in the block.

Answer 1

Given,

mass of bullet m =0.012 kg,

initial speed of bullet « = 70 m,

mass of wood block M =0.4 kg.

From conservation law of momentum mu = (M + m)v

v = mu / (M + m) = 0.012 x 70 / (0.4 + 0.012) = 2.04 m

If the block now rises to a maximum height of h, then using conservation law of mechanical energy,

we have

h = 0.212m = 21.2 cm