1.[1pt] A car, mass m 1 is moving to the right on a frictionless air track. It c
ID: 1265020 • Letter: 1
Question
1.[1pt]
A car, mass m1 is moving to the right on a frictionless air track. It collides with a second car, mass m2, which is initially at rest. Which of the following statements are true? (If A and E are true, and the others are not, enter TFFFT).
A) If car 1 is much lighter than m2, and the collision is perfectly elastic, car 1 will continue heading to the right with nearly its original speed after the collision.
B) If car 1 sticks to car 2, the final total kinetic energy of the car1-car2 system is less than the initial total kinetic energy of the two cars.
C) If the collision is elastic, car 1 must always come to a stop after the collision.
D) Suppose (for this statement only) that car 2 was NOT initially at rest, but was instead heading towards car 1 with equal (but opposite) momentum before the collision. After the collision, the cars must both be at rest.
E) If car 1 sticks to car 2, the car1-car2 system must move to the right after the collision.
Explanation / Answer
QUESTION:
A) If car 1 is much lighter than
m
2
, and the collision is perfectly elastic, car 1
will continue to the right with nearly its original speed after the collision.
B) If car 1 sticks to car 2, the car1-car2 system must be at rest after the collision.
C) If car 1 sticks to car 2, the final kinetic energy of the car1-car2 system is less
than the initial total kinetic energy of the two cars.
D) If the collision is elastic, car 1 must always come to a stop after the collision.
E) Suppose (for this statement only) that car 2 was NOT initially at rest, but
was instead heading towards car 1 with equal (but opposite) momentum before
the collision. After the collision, the cars must both be at rest.
ANSWER:
a) False. Car 1 will rebound in the opposite direction.
b) False. The system must move to preserve momentum.
c) True. KE not conserved in inelastic collisions.
d) False. It may, but not necessarily.
e) False. Momentum must be conserved, so if the cars had different masses, they
would not come to rest
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