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# Impulse and Restitution watch

1. I need some help understanding impulse and restitution, and i'm always getting stuck on question where you have to find speeds after particles or spheres have collided with walls.

e.g.

You know the impulse, 3Ns, you know the coefficient of restituion, 0.6, and you know the mass, 0.2, thus how do i find any of the velocities?
Oh and the sphere starts at rest and hits into a wall, with what velocity will it return to it's original position?

2. (Original post by rich_greeny)
I need some help understanding impulse and restitution, and i'm always getting stuck on question where you have to find speeds after particles or spheres have collided with walls.

e.g.

You know the impulse, 3Ns, you know the coefficient of restituion, 0.6, and you know the mass, 0.2, thus how do i find any of the velocities?
Oh and the sphere starts at rest and hits into a wall, with what velocity will it return to it's original position?

e=v/u and I=m(v-u),u know e,I and m and u want to find v and u,there are two eqns so simultaneous eqns should be your first thought.
3. (Original post by IntegralAnomaly)
e=v/u and I=m(v-u),u know e,I and m and u want to find v and u,there are two eqns so simultaneous eqns should be your first thought.

but haven't you got intial and final velocities for before and after the collision with the wall?
4. (Original post by rich_greeny)
but haven't you got intial and final velocities for before and after the collision with the wall?
thats what u and v are! u is the speed before impact and v is speed after impact,thats what the qu is asking for.

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