A 50gram lead bullet, specific heat 0.02 is initially at `30^(@)` C. It is fired vertically upwards with a speed of `840 m// s` . On returning to the starting level, it strikes a cake of ice at `0^(@)C`. How much ice is melted ? Assume that all energy is spent in melting ice only. Take latent heat of ice `= 80 cal. //` gram.

Answer

53

Explanation

Heat released by bullet = heat gained by ice
`rArr (1)/(2)mv^(2) +m_(1)S Delta theta = mL`
`rArr (1)/(2) xx (50 xx 10^(-3)) xx (840)^(2) xx (1)/(4.2) +50 xx 0.02 xx (30 -0) = m xx 80`
`m = 52.875 gm`