Further mechanics successive oblique impacts

I have the following question: Two cushions of a snooker table W1 and W2 meet at right angles. A snooker ball travels across the table and collides with W1 and then W2. The cushions are modelled as smooth. Just befor3 the first impact the ball is moving with speed u ms-1 at an angl3 of 20⁰ to W1. The coefficients of restitution between the ball and the cushions W1 and W2 are 1/2 and 2/5 respectively. Find the p3rcebtage if the balls original kinetic energy that is lost in the collisions.

The model answer uses a weird method I don't understand. But i used me own method to find w, however I end up with 0.485u and they get 0.413. Does anyone know where I went wrong or is able to explain a better method?

OP

Original post by Amy.fallowfield

I have the following question: Two cushions of a snooker table W1 and W2 meet at right angles. A snooker ball travels across the table and collides with W1 and then W2. The cushions are modelled as smooth. Just befor3 the first impact the ball is moving with speed u ms-1 at an angl3 of 20⁰ to W1. The coefficients of restitution between the ball and the cushions W1 and W2 are 1/2 and 2/5 respectively. Find the p3rcebtage if the balls original kinetic energy that is lost in the collisions.

The model answer uses a weird method I don't understand. But i used me own method to find w, however I end up with 0.485u and they get 0.413. Does anyone know where I went wrong or is able to explain a better method?

You calculate
w = 0.413u
Is it a typo at the end?

Reply 3

Amy.fallowfield

OP

11

Original post by mqb2766

Original post by Amy.fallowfield

I have the following question: Two cushions of a snooker table W1 and W2 meet at right angles. A snooker ball travels across the table and collides with W1 and then W2. The cushions are modelled as smooth. Just befor3 the first impact the ball is moving with speed u ms-1 at an angl3 of 20⁰ to W1. The coefficients of restitution between the ball and the cushions W1 and W2 are 1/2 and 2/5 respectively. Find the p3rcebtage if the balls original kinetic energy that is lost in the collisions.

The model answer uses a weird method I don't understand. But i used me own method to find w, however I end up with 0.485u and they get 0.413. Does anyone know where I went wrong or is able to explain a better method?