Question

A piece of taffy slams into and sticks to another identical piece of taffy that is at rest. The momentum of the two pieces stuck together after the collision is the same as it was before the collision, but this is not true of the kinetic energy, which is partly turned into heat. What percentage of the kinetic energy is turned into heat

Answer 1

Answer:0.5

Explanation:

Given

Piece of taffy slams in to sticks to another identical  piece and stuck into it.

Let m be the mass of taffy and u be the initial velocity of taffy and v be the final velocity of system.

Conserving momentum

$mu=2mv$

$v=\frac{u}{2}$

Initial kinetic energy$=\frac{mu^2}{2}$

Final Kinetic Energy$=\frac{2m(\frac{u}{2})^2}{2}=\frac{mu^2}{4}$

change in kinetic energy $\Delta K.E.=\frac{mu^2}{2}-\frac{mu^2}{4}=\frac{mu^2}{4}$

change in kinetic energy will contribute in heat energy

thus fraction of kinetic energy converted in to heat $=\frac{heat\ energy}{Initial\ kinetic\ Energy} =\frac{\frac{mu^2}{4}}{\frac{mu^2}{2}}=\frac{1}{2}=0.5$