Question

A 50 g bullet moving with velocity 10 m/s strikes a block of mass 950 g at rest and gets embedded in it. The loss in kinetic energy will be

• A. 100%
• B. 95%
• C. 5%
• D. 50%

Answer 1

Answer: (B)

95%

Answer 2

Initial K.E. of system = K.E. of the bullet =$\frac { 1 } { 2 } m _ { B } v _ { B } ^ { 2 }$

By the law of conservation of linear momentum

⇒ $v _ { \text {sys. } } = \frac { m _ { B } v _ { B } } { m _ { \text {sys. } } } = \frac { 50 \times 10 } { 50 + 950 } = 0.5 \mathrm {~m} / \mathrm { s }$

Fractional loss in K.E. =

By substituting $m _ { B } = 50 \times 10 ^ { - 3 } \mathrm {~kg} , v _ { B } = 10 \mathrm {~m} / \mathrm { s }$

we get

Fractional loss = $\frac { 95 } { 100 }$ ∴ Percentage loss = 95%