1. Glider A of mass 2.5 kg moves with speed 1.7 m/s on a horizontal rail without

Question

1. Glider A of mass 2.5 kg moves with speed 1.7 m/s on a horizontal rail without friction. It collides elastically with glider B, which is initially at rest. After the collision, the value of the speed of glider A is 0 m/s. What is the mass of glider B in kg? a. 1.7 b. 5 c. 1.3 d. 2.5 e. 0.5 An astronaut, floating weightlessly in orbit, shakes a bowling ball from side to side. She reports back to Earth that a. The shaking costs her no effort because the ball has no weight in space. b. The shaking costs her some effort and significantly more than on Earth. c. The shaking costs her some effort, but significantly less than on Earth. d. Although weightless, the inertial mass of the ball is the same as on Earth. e. The shaking costs a little bit more effort because she's in orbit. 2. A glider of mass 5.0 kg hits the end of a horizontal rail with a speed of 2 m/s and bounces off with the same speed, in the opposite direction. The collision is elastic and takes place in a time interval of 0.2s. What is the average force, in N, in the collision? a. 10 3. b. 50 c. 100 d. 250 e. 500

Explanation / Answer

1] The collision is elastic in nature. So, the momentum and kinetic energy of the system before and after the collision are conserved.

therefore,

2.5(1.7) + m(0) = 2.5(0) + mv

=> mv = 4.25 kgm/s

and (1/2)(2.5)(1.7)2 + 0 = 0 + (1/2)mv2

=> (1/2)mv2 = 3.6125 J

and (1/2)mv2 = (1/2)mv x v = (1/2)(4.25)v = 3.6125

=> v = 1.7 m/s

therefore, m = 4.25/1.7 = 2.5 kg [option d].

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