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Jack and Zack are standing on a crate at rest on a frictionless horizontal surface. Jack...

Jack and Zack are standing on a crate at rest on a frictionless horizontal surface. Jack has a mass of 70 kg, Zack has a mass of 45 kg, and the crate has a mass of 15 kg. In what follows, we will see that both jump of the crate. You may assume that they push themselves off with a speed of 4 m/s relative to the crate and in a direction that is essentially horizontal.

a) what is the final speed of the crate if Jack and Zack jump simultaneously, in the same direction?

b) what is the final speed of the crate if Jack and Zack jump simultaneously, in opposite directions?

c)what is the final speed of the crate if Jack jumps first and Zack jumps a few seconds later, in the opposite direction as Jack?

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