Question

heat

Answer 1

A 50 gm lead bullet, specific heat 0.02 is initially at 30*C .It is fired vertically upwards with a speed of 840 m/s and on returning to the starting level,strikes a cake at 0*C.How much ice is melted ?

Answer 2

assume there is no loss of energy and L heat of ice =80 cal/g

Answer 3

0.02 what unit ? Cannot be SI J/kg/K

Answer 4

no unit given must be cal

Answer 5

do post an answer ..i will be back in 15 min nw i hav to hav lunch

Answer 6

I will, then I'll have to go shopping. See you in a few hours.

Answer 7

0.02 must be cal/g/K

Answer 8

The bullet fired upwards with a certain velocity falls back with the same one, since we don't have air resistance in the world of elementary physics. It strikes the ice on its way down and its kinetic energy converts to thermal energy.

Notice that the bullet is hotter than the ice even originally (it is at 30*C). It loses a little bit of heat to make its temperature zero and also the kinetic energy it had.

So, your first move would be to calculate that energy lost, the kinetic energy and the heat energy. That much heat is available for the ice to melt. Since each gram of ice that 80 cal per gram, you should be able to calculate how many grams of ice melt.

Be aware that ice is only changing phase, not temperature. Unless all the ice melts, heat will do nothing other than melt more ice.