Question

A 20 g bullet passes through a plate of mass 1 kg and finally comes to rest inside another plate of mass 2980 g. It makes the plates move from rest to same velocity. The percentage loss in velocity of bullet between the plate is

• A. 0
• B. 50 %
• C. 75 %
• D. 25 %

Answer 1

Answer: (D)

25 %

Answer 2

Using conservation of momentum

0.02 u = 0.02 v +1V₁ …….. (i)

(where V₁ be the velocity of plate of 1 kg)

and 0.02 v = (2.98 + 0.02)V₁ ………. (ii)

( plate of 3 kg has also same velocity i.e., V₁)

or V₁ = 0.02

Substituting

∴ 0.02 v = 0.02 + 0.02 $\frac { \mathrm { v } } { 3 }$

or v = or v =

% age loss in velocity = $\frac { v - u } { u } \times 100$

= $\frac { v - \frac { 3 } { 4 } v } { v } \times 100$ = 25%