A Lambda particle Λ decays into a proton p and a pion π, Λ → p + π, and it is observed that the proton is left at rest. (a) What is the energy of the pion? (b) What was the energy of the Lambda particle? Derive your results analytically and then calculate the answers using mΛ = 1116 MeV, mp = 938 MeV, mπ = 140 MeV (masses are expressed in units c = 1).

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 77.4 kg , but she is unsure of the mass of a large gas canister in the airless rocket. when this canister is approaching her at 3.50 m/s , she pushes against it, which slows it down to 1.30 m/s (but does not reverse it) and gives her a speed of 2.60 m/s . what is the mass of the canister?