An astronaut in space cannot use a scale or balance to weigh objects because the

Question

An astronaut in space cannot use a scale or balance to weigh objects because there is no gravity. But she does have devices to measure distance and time accurately. She knows her own mass is 85.9kg , but she is unsure of the mass of a large gas canister in the airless rocket. When this canister is approaching her at 3.80m/s , she pushes against it, which slows it down to 1.10m/s(but does not reverse it) and gives her a speed of 2.00m/s .

I found the mass=63.6kg but for "How much kinetic energy is

Explanation / Answer

conservation of momentum

m*3.8 = m*1.1   + 85.9*2

m = 63.629 kg canister mass

change in kinetic energy = final - initial = (0.5*85.9*2*2 + 0.5*63.629*1.1*1.1)-(0.5*63.629*3.8*3.8) = - 249.105 Joules ( sign indicates loss )

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