81. Two masses collide and stick together. Before the collision : 2102132
81. Two masses collide and stick together. Before the collision one of the masses was at rest. Is there a situation in which the kinetic energy is conserved in such a collision?
A. Yes, if the less massive particle is the one initially at rest.
B. Yes, if the more massive particle is the one initially at rest.
C. Yes, if the two particles have the same mass.
D. No, kinetic energy is always lost is such a collision.
82. In an automobile collision, how does an airbag lessen the blow to the passenger? Assume as a result of the collision, the passenger stops.
A. The air bag decreases the momentum change of the passenger in the collision.
B. During the collision, the force from the air bag is greater than would be the force from the windshield or dashboard so the passenger cannot hit the hard objects.
C. The stopping impulse is the same for either the hard objects or the airbag. Unlike the windshield or dashboard, the air bag gives some increasing the time for the slowing process and thus decreasing the average force on the passenger.
D. The airbag is there to insure the seatbelt holds.
83. Two masses m1 and m2, with m1 = 3 m2, undergo a head-on elastic collision. If the particles were approaching with speed v before the collision, with what speed are they moving apart after collision?
A. 3 v
84. Two masses m1 and m2, with m1 < m2, have momenta with equal magnitudes. How do their kinetic energies compare?
A. KE1 < KE2
B. KE1 = KE2
C. KE1 > KE2
D. More information is needed.
85. Two particles collide, one of them initially being at rest. Is it possible for both particles to be at rest after the collision?
A. If the collision is perfectly inelastic, then this happens.
B. If the collision is elastic, then this happens.
C. This can happen sometimes if the more massive particle was at rest.