P1. Two identical objects A and B of mass M move on a one-dimensional, horizonta
ID: 1399243 • Letter: P
Question
P1. Two identical objects A and B of mass M move on a one-dimensional, horizontal air track. Object B initially moves to the left with speed vo. Object A initially moves to the right with speed 3vo, so that it collides with object B. Friction is negligible. Express your answers to the following in terms of M and vo.
(a) Determine the total momentum of the system of two objects.
(b) A student predicts that collision will be totally inelastic (the objects stick together on collision). Assuming this is true, determine the following for the two objects immediately after the collision. i. the speed ii. the direction of motion.
I 'm having trouble in how to approach the problem, specifically when to use inelastic or elastic.
Explanation / Answer
before collision
mA = M
vA = 3vo ( right )
mB = M
vB = -vo ( left )
momenutm of A = pA = mA*vA = 3*M*vo
momentum of B = PB = mB*vB = -M*vo
total momentum of the system of two objects = Pi = PA + pB
Pi = 3*M*vo - M*vo
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part(b)
after collision the two objects stick together
let V be their common velocity
final momentum = Pf = (mA+mB)*v = 2M*V
from momentum conservation the total momentum of the system remains constant in any collision
Pf = Pi
2*M*v = 3*M*vo - M*vo
2V = 2vo
v = vo
ii)
the final speed v = +vo
the two objects moves towards right after collision
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