- #1

kshitij

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- Homework Statement
- A ball of mass m1 is moving with velocity 3v. It collides head on elastically with a stationary ball of mass m2 . The velocity of both the balls become v after collision. Then the value of the ratio m2/m1 is

- Relevant Equations
- Conservation of momentum, Conservation of energy

Since in an elastic collision, both momentum and energy is conserved,

P(initial)=P(final)

m1(3v)=m1v+m2v

m2/m1=2

Which was the given answer but if we use conservation of energy,

K.E(initial)=K.E(final)

1/2*m1*(3v)^2=1/2*m2*v^2+1/2*m1*v^2

m2/m1=8

Why do we get two different answers and why doesn't conservation of energy gives us the right answer here?

P(initial)=P(final)

m1(3v)=m1v+m2v

m2/m1=2

Which was the given answer but if we use conservation of energy,

K.E(initial)=K.E(final)

1/2*m1*(3v)^2=1/2*m2*v^2+1/2*m1*v^2

m2/m1=8

Why do we get two different answers and why doesn't conservation of energy gives us the right answer here?