A ball is thown horizontally from a train station platform directly into the pat

Question

A ball is thown horizontally from a train station platform directly into the path of a huge locomotive traveling in the opposite direction. Assume the ball strikes the front of the locomotive at a perfectly flat and vertical location. Also assume the initial velocities of the ball and locomotive relative to the observer standing on the train station platform are 7 m/s and 119 m/s respectively. Determine the speed of the tennis ball relative to the observer standing on the station platform in m/s if (a) perfect elastic collision occurs, (b) perfect plastic collision occurs and (c) coefficient of restitution of collision =

Explanation / Answer

Part A:

v1 = { [m1 - m2] / [m1 + m2] }* u1 + { 2 m2 / [m1 + m2]} * u2

v2 = { 2 m1 / [m1 + m2]} * u1 +  { [m2 - m1] / [m1 + m2] }* u2

u1 = 7 m/s; u2 = -119 m/s;

The velocity of the tennis ball, v1 = v1 = { [m1 - m2] / [m1 + m2] }* 7 m/s - { 2 m2 / [m1 + m2]} * 119 m/s

As, m1 << m2; m1 - m2 = -m2; &  m1 + m2 = m2;

v1 = (-m1/m1)*7 - (2m1/m1)*119 = -245 m/s

The velocity of the tennis ball, v1 = -245 m/s (-ve sign indicates the ball moves same as the direction of locomotive)

Part B:

In a perfectly plastic collision, both the objects stick together.

Hence, the ball moves with a speed same as that of the speed of the locomotive i.e., = -119 m/s

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.