a hockey puck is moving at a velocity of 5.5 m/s (it weighs.025 kg) it strikes a

Question

a hockey puck is moving at a velocity of 5.5 m/s (it weighs.025 kg) it strikes another puck that is at rest(it weighs .050 kg)the first puck takes the direction of 65 degrees above thehorizontal, and the second puck takes the direction of 37 degreesbelow the horizontal, what are the final speeds of each puck? have trouble setting this problem up a hockey puck is moving at a velocity of 5.5 m/s (it weighs.025 kg) it strikes another puck that is at rest(it weighs .050 kg)the first puck takes the direction of 65 degrees above thehorizontal, and the second puck takes the direction of 37 degreesbelow the horizontal, what are the final speeds of each puck? have trouble setting this problem up

Explanation / Answer

In order to solve this problem you first have to assume that thecollision is perfectly elastic, that is that no kinetic energy islost or converted to any other form of energy during thecollision. The law of conservation of momentum states that the net momentumbefore the collision will equal the net momentum after thecollision. Since momentum can be represented by vectors, youcan use vector addition and subtraction to arrive at theanswer. Hockey puck A has a momentum vector (we are assuming that itstraveling directly to the right) of = Hockey puck B has a momentum vector of because it's atrest. after the collision, we can say that (based on the x and ycomponents of the momenta and the angle of direction): M will be the momentum of the first puck, N will be of thesecond A will have a vector of and B willhave a vector of the x components of all the momentum should be equal to before thecollision (as should the Y components): .1375 = cos(65)*M + cos(-37)*N 0 = sin(65)*M + sin(-37)*N .1375 = .4226M + .7986N 0 = .9063M + -.6018N rearrange the second equation: M = .66401 N and plug it into the first equation: .1375 = .422(.66401N) + .7986N N = .12745 newton meters and then solve for M: M = .66401(.12745) = .0846 newton meters now divide by their masses and you'll get the speeds: speed of puck A = M/.025 = 3.384 m/s speed of puck B = N/.05 = 2.483 m/s

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