# PHYSICS HELP! (INELASTIC VS ELASTIC COLLISIONS) ****10 POINTS****?

A small block of mass 2.0 kg is released from rest at the top of the curved frictionless ramp as shown above. The block slides down the ramp and is moving with a speed of 3.5 m/s when it collides with a larger block of mass 3.0 kg at rest at the bottom of the incline. The larger block moves to the right at a speed of 2.0 m/s immediately after the collision.

a) Determine height (h) of the ramp from which the small box was released

b)Determine the speed of the small block (2.0 kg) after the collision

c)The larger block slides a distance of 1.0 m before coming to rest. Determine the value of the coefficient of kinetic friction, between the larger block and the surface on which it slides.

d)Indicate whether the collision between the two blocks is elastic or inelastic. Justify your answer.

Relevance

a) KE before impact = 0.5*m*v^2 = 0.5*2*3.5^2 = 12.25 J = m*g*h

so h = 12.25 / (2*9.8) = 0.625 m

b) Momentum is conserved in all collisions.

Total momentum = m*v = 2.0*3.5 = 7.0 kg.m/s (to right)

Momentum of larger block after impact = 3.0*2.0 = 6.0 kg.m/s (to right)

so momentum of small block after impact = 7.0 - 6.0 = 1.0 kg.m/s (to right)

so speed of small block after collision = 1.0 kg.m/s / 2.0 kg = 0.5 m/s (to right)

c) v^2 - u^2 = 2a*s

v = 0, u = 2.0m/s, s = 1.0m

so acceleration is a = -2.0^2 / 2*1.0 = -2.0 m/s^2 = -μk*g

so μk = 2.0 / 9.8 = 0.204

d)

Total KE before collision = 0.5*2.0*3.5^2 = 12.25J

Total KE after collision = (0.5*2.0*0.5^2) + (0.5*3.0*2.0^2) = 0.25+6 J = 6.25J

Energy is not conserved

So the collision is inelastic

• An inelastic collision is one wherein no power is lost using collision. interior the authentic international, there is not any such component as a splendidly inelastic collision, yet many physics issues are very close, the main easy situation being that of "billiard balls rolling on a frictionless floor". (whether there have been a frictionless floor, universal billiard balls create some frictional warmth and sound while they collide.) usually speaking, for physics issues that arise in a classification, if the products do no longer stick jointly, you may assume that the collision is inelastic.