InterviewSolution
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InterviewSolution
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Two hockey players of opposite teams, while trying to hit a hockey ball on the ground collide and immediately become entangled. One has a mass of 60 kg and was moving with a velocity 5.0 m s^(-1) while the other has a mass of 55 kg and was moving faster with a velocity 6.0 m s^(-1) towards the first player. In which direction and with what velocity will they move after they become entangled ? Assume that the frictional force acting between the feet of the two players and ground is negligible. |
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Answer» Solution :Let the first player be moving from left to right. By CONVENTION left ot rightis taken as the positivedirection and thus right to left is th E negative direction. If symbols m and u represent the mass and initial velocity of the two players, respectively. Subscripts 1 and 2 in these physical quantities refer to teh two hockey players Thus, `m_(1) = 60 kg , u_(1) = + 5 ms^(-1), and m_(2) = 55 kg` `u_(2) = - 6 ms^(-1)` The total momentum of the two players before the collision = 60 kg ` xx ( + 5 ms^(-1)) + 55 kg xx (- 6 ms^(-1))` ` = -30 kg ms^(-1)` If v is the velocity of the two entangled players after the collision, the total momentum then ` = (m_(1) + m_(2)) xx v` ` = (60+ 55) kg xx v ms^(-1)` ` = 115 xx v kg ms^(-1)`   Equating the momenta of the system before and after collision, in ACCORDANCE with the law of conservation of momentum, we get ` v = - (30)/(115)` ` = -0.25ms^(-1)` Thus, the two entangled players would move with velocity 0.26 m `s^(-1)` from right to left, that is in the direction the second player was moving before the collision. |
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