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Standard XII

Physics

Average and Instaneous Power

A lead bullet...

Question

A lead bullet of mass 21 g travelling at a speed of $100 m s^{- 1}$ comes to rest in a wooden block. If no heat is taken away by the wood, then find the raise in temperature of wood specific heat of $l e a d = 0.03 c a l o r i e / g^{\circ} C$

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Solution

Given that,

Rise temperature $= Δ T$

Mass of the bullet $= m$

Now, the kinetic energy associated with the bullet

$K . E = \frac{1}{2} m v^{2}$

$K . E = \frac{1}{2} \times 0.021 \times {(100)}^{2} = 105 J$

Now, according to law of conservation of energy

Change in kinetic energy of bullet = change in internal energy of wood

$K . E = m s Δ T$

$Δ T = \frac{K . E}{m s} = \frac{105 J}{21 \times 0.03 \times 4.2} = 39.68^{o} C$

Hence, the rise temperature of bullet is $39.68^{o} C$

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A lead bullet of mass 21 g travelling at a speed of 100ms−1 comes to rest in a wooden block. If no heat is taken away by the wood, then find the raise in temperature of wood specific heat of lead=0.03 calorie/g∘C

A lead bullet of mass 21 g travelling at a speed of $100 m s^{- 1}$ comes to rest in a wooden block. If no heat is taken away by the wood, then find the raise in temperature of wood specific heat of $l e a d = 0.03 c a l o r i e / g^{\circ} C$