Question

A bullet having a mass of 10 g and moving with a speed of 1.5 m/s, penetrates a thick wooden plank of mass 90 g. The plank was initially at rest. The bullet gets embedded in the plank and both move together. Determine their velocity.(Ans: 0.15 m/s). Solve the example.

Answer 1

Given in the question .
$Mass_(bullet) = 10 g$ or 0.01 kg
$Velocity_(bullet) = 1.5 m/sec$
$Mass_(plank) = 90 g .$ or 0.09 kg.

Therefore, Momentum before Collison.
$Mass_b_u_l_l_e_t * velocity$ + $Mass_p_l_a_n_k * velocity$
Therefore putting the values,
= (0.01 x 1.5) + ( 0.09 x 0)
⇒ 0.015 kgm/s

Now, After collison momemtum.
$Mass_b_u_l_l_e_t * velocity$ + $Mass_p_l_a_n_k * velocity$
Putting values here
= $(0.1 ) * v$
⇒ 0.1 v kgm/s

Therefore,
momentum before collision is equal to momentum after collison.
$0.015 = 0.1 v$
Hence , v = 0.15 m/sec.


Hope it Helps.