Posted by **Anonymous** on Saturday, November 6, 2010 at 2:44pm.

A 5.00 g object moving to the right at +20.0 cm/s makes an elastic head-on collision with a 10.0 g object that is initially at rest.

(a) Find the velocity of each object after the collision.

5.00 g object cm/s

10.0 g object cm/s

(b) Find the fraction of the initial kinetic energy transferred to the 10.0 g object.

%

- Physics -
**Damon**, Saturday, November 6, 2010 at 3:50pm
momentum before = 5*20 = 100

momentum after = 100 = 5 v1 + 10 v2

Ke before = (1/2)5(400) = 1000

Ke after = 1000 = .5*5*v1^2 + .5*10*v2^2

or

2000 = 5 v1^2 + 10 v2^2

but v2 = (100-5v1)/10 = (10 -.5v1)

v2^2 = 100-10v1+.25v1^2

so

2000 = 5v1^1 + 10(100-10v1+.25v1^2)

solve quadratic for v1. That is it, go back and get v2 and the kinetic energies.

Now we did that all in cgs system rather than meters, kilograms, seconds. I assume you are using an old text. Your energies will be in dynes rather than joules for that reason.

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