Jack and Jill are standing on a crate at rest on the frictionless, horizontal su

Question

Jack and Jill are standing on a crate at rest on the frictionless, horizontal surface of a frozen pond. Jack has a mass of 75.4kg , Jill has a mass of 45.3kg , and the crate has a mass of 15.0kg . They remember that they must fetch a pail of water, so each jumps horizontally from the top of the crate. Just after each jumps, that person is moving away from the crate with a speed of 4.50m/s relative to the crate. What is the final speed of the crate if Jack jumps first and then a few seconds later Jill jumps in the same direction? What is the final speed of the crate if Jill jumps first and then Jack, again in the same direction?

Explanation / Answer

when jack jumps with 4.5 away from crate

v2 is the speed of the crate

m1V1+m2*v2 = 0

when jill jumps from the crate
v3 is speed of crate

-75.4*4.5 + (45.3+15)*v2 =0

v2 = 5.626 m/s

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