ame Quiz 2 A 1. In a perfectly inelastic one-dimensional collision between two o

Question

ame Quiz 2 A 1. In a perfectly inelastic one-dimensional collision between two objects, what initial condition alone is necessary so that all of the original kinetic energy of the system is gone after the collision? A. The objects must have the same mass. B. The objects must have the same velocity. C. The objects must have the same speed, with velocity vectors in opposite directions. D. The objects must have momenta with the same magnitude but opposite directions. 2. A billiard ball rolling across a table at 1.30 m/s makes a head-on elastic collision with an identical bal. Find the speed of each ball after the colision if the second ball is moving toward the first at a speed of 1.15 m/s. 3. A car with mass 1.60x103 kg traveling east at a speed of 21.3 m/s collides at an intersection with a 2.44x10 kg van traveling north at a speed of 18.5 m/s, as shown in the figure. Find the magnitude and direction of the velocity of the wreckage after the collision, assuming that the vehicles undergo a perfectly inelastic collision (that is, they stick together) and assuming that friction between the vehicles and the road can be neglected.

Explanation / Answer

1. (D)

p1 = - p2

from mommentum conservation,

pi = pf

(p1 + p2) = (m1 + m2) v

- p2 + p2 = (m1 + m2) v => v = 0

2. for same mass elastic collision, velocities get exchanged.

v2f = v1i and v1f = v2i

speed of 1st ball = 1.15 m/s in opposite direction.

speed of 2nd ball = 1.30 m/s in opposite direction.

3. pi = pf

(1.60 x 10^3 x 21.3)i + (2.44 x 10^3 x 18.5)j = (1.60 x 10^3 + 2.44 x 10^3) v

v = 8.44i + 11.2 j m/s

magnitdue = sqrt(8.44^2 + 11.2^2) = 14 m/s ....Ans

direction = tan^-1(11.2 / 8.44) = 53 deg North of east

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