On a cold winter day, a penny (mass 2.50 g ) and a nickel (mass 5.00 g ) are lyi

Question

On a cold winter day, a penny (mass 2.50 g) and a nickel (mass 5.00 g) are lying on the smooth (frictionless) surface of a frozen lake. With your finger, you flick the penny toward the nickel with a speed of 2.15m/s .

1) The coins collide elastically; calculate both their final speeds.

vpenny, vnickel = _____ m/s

Two cars collide at an intersection. Car A, with a mass of 1800kg , is going from west to east, while car B, of mass 1500kg , is going from north to south at 13.0m/s . As a result of this collision, the two cars become enmeshed and move as one afterwards. In your role as an expert witness, you inspect the scene and determine that, after the collision, the enmeshed cars moved at an angle of 55.0? south of east from the point of impact.

1)How fast were the enmeshed cars moving just after the collision?

v =_____ m/s

2) How fast was car A

going just before the collision?

Explanation / Answer

1)

By the law of momentum conservation:-
=>m1u1 + m2u2 = m1v1 + m2v2
=>2.50 x 10^-3 x 2.15 + 0 = 2.50 x 10^-3 x v1 + 5.0 x 10^-3 x v2
=>5.38 = 2.5v1 + 5v2
=>v1+2v2 = 2.15 ------------------(i)
for elastic collision:-
=>v1 - v2 = u2 - u1
=>v1 - v2 = -2.15 -----------------(ii)
=>By (i) + 2 x (ii):-
=>3v1 = -2.15
=>v1(penny) = -0.72 m/s [-ive indicating the direction is opposite to the initial velocity of penny]
By (ii) :-
=>v2(nickel) = 1.43 m/s[-ive indicating the direction is same to the initial velocity of penny]

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