I have tried long and hard on this question and it is the last one i have to do before the assignment is finished.(adsbygoogle = window.adsbygoogle || []).push({});

Two identical spheres collide. One is at rest on a horizontal surface, the other drops vertically. The collision is as shown (see attatchment). After the collision, both spheres move horizontally. What is the apparrent coefficient of restitution.

Now we cannot use conservation of momentum in the y direction, or the normal direction, as an external force from the surface will act. We can use it however in the x direction, and by doing this you get;

v'A=-v'B

furthermore, by using the equation for the tangential direction of the collision we get;

tan(23) = (v'A)/(vA)

here i have used a tangential normal sytem and my dynamics lecturer insists what i have above is all that is required to solve the problem when you apply it to the equation;

e = (v'B-v'A)/(vA-vB)

which simplifies to

e = (v'B-v'A)/(vA)

However, when i apply all that i have found as above, i get the top line of above equal to zero, and i can assure you this is not the correct answer.

Clearly i have attmepted this question and i am unfortunately stuck. perhaps someone could help me....

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# Homework Help: Dynamics Problem

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