Example 9.8 - Chapter 9 Class 9 - Force and Laws Of Motion (Term 1)
Last updated at June 3, 2019 by Teachoo
Examples from NCERT Book
Last updated at June 3, 2019 by Teachoo
Example 9.8 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 & 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 become entangled? Assume that the frictional force acting between the feet of the two players & ground is negligible. Given Mass of player 1 = m1 = 60 kg Velocity of player 1 = u1 = 5 m/s Mass of player 2 = m2 = 55 kg Velocity of player 2 = u2 = −6 m/s Velocity u2 is negative since his direction is opposite to that of u1 After collision, Mass of the system = m1 + m2 = 60 + 55 = 115 kg Let the velocity after collision = v Momentum before Momentum = Momentum of Player 1 + Momentum of Player 2 = 60 × 5 + 55 (−6) = 300 − 330 = −30 kg m/s Momentum after Momentum = Total Mass × Velocity After = (m1 + m2) × v = 115v Since momentum is conserved, Total momentum before collision = Total momentum after collision − 30 = 115v (−30)/115 = v v = (−30)/115 v = −0.26 m/s Since velocity is in negative, it means after collusion both players will move from right to left