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JUST DO PART E ONLY PLEASE. Mech CONSERVATION OF MOMENTUM HW-2 3. Two astronauts

ID: 1523459 • Letter: J

Question

JUST DO PART E ONLY PLEASE.

Mech CONSERVATION OF MOMENTUM HW-2 3. Two astronauts, astronauts A and B, participate in three collision experiments in a weightless, frictionless environment. In each experiment, astronaut B is initially at rest, and astronaut A has 20 kg m/s to the rig t. (The velocities of the astronauts are measured al momentum with respect to a nearby space station.) Before After Experiments l, 2, 3 20 kg m/s at rest at rest The astronauts push on each other in different ways so that the outcome of each experiment is different. As shown in the figure at right, astronaut A has a different final momentum in each experiment a. Determine the magnitude of the final momentum of astronaut B in each experiment Explain 5 kg m/s b. Rank the final kinetic energy of astronaut B in the three experiments. Explain e. Is the total kinetic energy after the collision in Experiment 2 greater than, less than, or equal to the total kinetic energy after the collision in Experiment 3 al kinetic energy means the sum of the kinetic energies of the two astronauts.) Explain d. Consider the following statement: "The momentum of the system is conserved in each experiment because there is no net force on the system. If momentum is conserved, then kinetic energy must also be conserved, because both momentum and kinetic energy are made up of mass and velocity One of the sentences above is completely correct. Discuss the error(s) in reasoning in the other sentence. Tutorials in Introductory Physics McDermott, Shaffer, & P.E.G., U.Wash 2003

Explanation / Answer

3

a)

Case 1 :

using conservation of energy

Pbefore = Pafter

20 + 0 = 0 + Pb

Pb = 20

Case 2 :

using conservation of energy

Pbefore = Pafter

20 + 0 = - 5 + Pb

Pb = 25

Case 3 :

using conservation of energy

Pbefore = Pafter

20 + 0 = 5 + Pb

Pb = 15

b)

raking of momentum is given as

case 2 > case 1 > case 3

hence ranking of kinetic energy

case 2 > case 1 > case 3

d

the correct sentence is " the momentum is of the system is conserved in each experiment because there is no net force on the system"

the kinetic energy may or may not be conserved depending on the type of collision