How to Calculate Kinetic Energy Loss in a Collision

[richardnumber]

kinetic energy question!

hey,

I have the following question to complete, and don't have the slightest clue where to start! :(

A sphere of mass 1kg, moving at 10 m/s, overtakes another sphere of
mass 5 kg moving in the same line at 3m/s. Find the loss of kinetic
energy during impact, and show that the direction of motion of the
first sphere is reversed. Assume the coefficient of restitution e = .75

should i use the following formula?: 2(m1 + m2)E = m1m2(u1-u2)2(1-e2)

any help would be greatly appreciated,

Rich

Homework Equations

The Attempt at a Solution

 

[ideasrule]

Start by doing the first question: the loss in kinetic energy. Since the coefficient of restitution is 0.75, 25% of the initial kinetic energy is lost, correct?

Then write out the conservation of momentum & conservation of energy equations, remembering that 25% of the original kinetic energy is lost.

 

[Doc Al]

should i use the following formula?: 2(m1 + m2)E = m1m2(u1-u2)2(1-e2)

I don't recognize that formula. In any case, it's usually best to derive your own formula from first principles.

Hint: What's the definition of the coefficient of restitution? That will give you one equation. Conservation of momentum will give you the other.

 

[Redbelly98]

Start by doing the first question: the loss in kinetic energy. Since the coefficient of restitution is 0.75, 25% of the initial kinetic energy is lost, correct?

Just a friendly correction, that isn't what is meant by coefficient of restitution; it involves the relative velocities of the objects before and after the collision. Presumably it's in the OP's textbook or lecture notes so I will reiterate Doc Al's advice and let the OP look it up.