# Physic "collisions and energy"

#### dorjiako

Question said: A 10kg block starts from rest at a height of 20m and slides down a frictionless, semicircular track. The block collides with a stationary object of 50kg at the bottom of the track. If the objects stick together upon collision, what is the maximum height that the block-object system could reach? I got the above solution.
However, follow up question said: In the above question, determine the height reached by each object if the collisin were inelastic and the falling mass rebounded back with a speed of 1m/s?
I was able to figure out that the height for the rebounded mass (10kg) is 0.051m using v^2 = 2as. s=1/(2x9.8). However, I couldn't the right answer for the height of remaining 50kg object?
Any help will be greatly appreciated.

#### FutureDoctor503

##### A.W.E.S.O.M.-O
5+ Year Member
Question said: A 10kg block starts from rest at a height of 20m and slides down a frictionless, semicircular track. The block collides with a stationary object of 50kg at the bottom of the track. If the objects stick together upon collision, what is the maximum height that the block-object system could reach? I got the above solution.
However, follow up question said: In the above question, determine the height reached by each object if the collisin were inelastic and the falling mass rebounded back with a speed of 1m/s?
I was able to figure out that the height for the rebounded mass (10kg) is 0.051m using v^2 = 2as. s=1/(2x9.8). However, I couldn't the right answer for the height of remaining 50kg object?
Any help will be greatly appreciated.
You can find the height of 50kg object by using the following equation:

(m)(g)(h final) = (0.5)(m)(v final)^2 assuming KE is conserved

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#### dorjiako

I am probably making mistake on the actual value of the final velocity. So, what is the velocity to be used in this problem?
Thanks.