A skier is coasting down a hill with a speed v when suddenly her arm falls off.

Question

A skier is coasting down a hill with a speed v when suddenly her arm falls off. What happens to the skier's speed if momentum is conserved? It remains constant. It decreases. It increases. Wait, did you just say her arm fell off? Two children float motionlessly in a space station. The 20 kg girl pushes on the 40kg boy and he sails away at 1.0 m/s. The girl remains motionless moves in the same direction at 1.0 m/s moves in the opposite direction at 1.0 m/s moves in the opposite direction at 2.0 m/s none of the above Inelastic and elastic collisions are similar in that momentum and kinetic energy are conserved in both momentum is conserved in both momentum and potential energy are conserved in both kinetic energy is conserved in both. Object 1has twice the mass of object 2 but the same (nonzero) kinetic energy, which has the greater momentum? Assume they are going in the same direction. Object 1 They have the same momentum Object 2 There is no way to tell

Explanation / Answer

1. B. It increases.

since, momentum is product of mass and velocity and remains constant unless an external force acts on the body. In the skier case, her arms falls off and therefore her mass decreases. So her speed must increase in order to keep the momentum same.

2. d. moves in opposite direction at 2.0 m/s

from the conservation of momentum, the boys and girls momentum must be equal and opposite in order to cancel the momenta.

momentum of the boy = 40kg*1.0 m/s = 40 kgm/s

therefore, momentum of the girl will be 40 kgm/s = 20 kg* v (in opposite direction)

    v= 40/20 = 2.0 m/s. in opossite direction.

3. b. momentum is conserverd in both.

in elastic collision both momentum and energy is conserved but in inelastic collision only momentum is conserved.

4. a. object 1

m1= 2m2

and,     0.5 m1v2 = 0.5 m2u2

putting m1 = 2m2 in energy equation

          m2v2 = 0.5 m2 u2

                u = 1.414 v

momentum of m1 = m1v

momentum of m2 = m2u = 0.5 m1* 1.414 v = 0.707 m1v

therefore momentum of object 1 is greater.

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