Calculating energy lost in collisions?

[pebbles]

My notes don't provide an equation.

I am given inital and final velocity
Vi=50 m/s
Vf=25 m/s

Thanks.

[dynamicsolo]

My notes don't provide an equation.

I am given inital and final velocity
Vi=50 m/s
Vf=25 m/s

Thanks.

I'm afraid it's worse than that: if you're trying to do an energy calculation, you're going to need a mass as well... If this is a collision problem, you're going to need both masses and the initial and final velocities for each of them.

Are you covering linear momentum in your course right now?

[pebbles]

oops forgot to note the masses: each is is 1 kg.

sorry!

[dynamicsolo]

Is what you posted originally the initial and final speed of both masses? There still seems to be detail missing from this problem.

In any case, you'll need the formula for kinetic energy. Find the sum of the kinetic energies of the two masses before the collision and compare it to the sum of their kinetic energies afterwards.

[pebbles]

agh. no!
what was i thinking?!
ok mass 1= 1.0 kg; initial velocity = 50; final velocity =25
mass 1.0 kg; initial velocity= 0; final velocity = 25

[dynamicsolo]

agh. no!
what was i thinking?!
ok mass 1= 1.0 kg; initial velocity = 50 m/sec ; final velocity =25 m/sec
mass 1.0 kg; initial velocity= 0; final velocity = 25 m/sec

It looks like you now have all the data assembled. How you do calculate the kinetic energy of an object? Find the initial and final kinetic energy for each mass and the total initial and final kinetic energies of the pair.