A 320-g air track cart traveling at 1.25 m/s suddenly collides elastically with a stationary 270-g cart.What is the speed of the 270-g cart just after the collision?
A)0.678 m/s
B)0.106 m/s
C)1.36 m/s
D)1.14 m/s
E)2.72 m/s

Question

Quizplus · Accepted Answer

Since the collision is elastic, we can use conservation of momentum and conservation of kinetic energy. 
Initial momentum = final momentum 
(320g)(1.25 m/s) = (270g)(v2)
v2 = (320/270)(1.25) = 1.48 m/s (velocity of the 270g cart just after collision)
Using conservation of kinetic energy: 
1/2(320g)(1.25 m/s)^2 = 1/2(270g)(v2)^2
1.5625 J = 0.5(270/320)v2^2
v2^2 = (2*1.5625*320)/(270) = 3.70 m^2/s^2
v2 = sqrt(3.70) = 1.36 m/s. 
Thus, the speed of the 270-g cart just after the collision is 1.36 m/s.

A 320-G Air Track Cart Traveling at 1