Question

State the Skate was an avid physics student whose main non-physics interest in life was high-speed skateboarding. In particular, Nate would often don a protective suit of Bounce-Tex, which he invented and after working up a high speed on his skateboard, would collide with some object. In this way, he got a gut feel for the physical properties of collisions and succeede3d in combining his two passions. On one occasion, the Skate, with a mass of 119 kg, including his armor, hurled himself against a 885-kg stationary and Nate bounced backward. What were Nate's speeds immediately before and after the collision? (Enter positive numbers.) Ignore friction with the ground. By the way, this brief bio of Nate the Skate is written in the past tense, because not long ago he forgot to put on his Bounce-Tex before colliding with the Washington Monument in a perfectly inelastic collision. We will miss him.

Answer 1

Perfectly elastic collision condition.

Let the speed before collision = u and after collision = v

Momentum balance equation:

119*u = 885*(1.13) - 119*v

    => u + v  = 8.4  ...........eqn(i)

Kinetic energy balance equation:

(1/2)*119*(u)^2 = (1/2)*885*(1.13)^2 + (1/2)*119*(v)^2

=> (u+v)*(u-v) = 9.5

=> u - v  = 1.13 ...........eqn(ii)

On solving eqn(i) and eqn(ii), we get:

Speed before collision  = u  = 4.76 m/s

  Speed after collision  = v  = 3.64 m/s