Question

A ball with a mass of `7 kg` and velocity of `1 m/s` collides with a second ball with a mass of `6 kg` and velocity of `- 5 m/s`. If `75%` of the kinetic energy is lost, what are the final velocities of the balls?

Answer 1

The final velocity is `=1.74 ms^(-1)`

Explanation:

Kinetic Energy `=1/2mv^2`
KE of first ball `=1/2*7*1^2=3.5J`
KE of second ball `=1/2*6*25=75J`
Total KE before collision `=78.5J`
Energy remaining after collision `=25/100*78.5=19.625J`
Total mass `=13 kg`
`E=1/2mv^2` `=>` `19.625=1/2*13*v^2`
So `v^2=(19.625*2/13)`
Final velocity `sqrt(19.625*2/13)=1.74 ms^(-1)`