Question
Nate 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 Inverted 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 succeeded in combining his two passions.* On one occasion, the Skate, with a mass of 113. kg, including his armor, hurled himself against a 821-kg stationary statue of Isaac Newton in a perfectly elastic linear collision. As a result, Isaac started moving at 1.93 m/s and Nate bounced backward, What were Nate's speeds immediately before and after the collision? (Enter positive numbers.) Ignore friction with the ground.
Explanation / Answer
conservation of momentum
m1u1 + m2u2 = m1v1 + m2v2
113* u1 + 0 = 821*1.93 - 113*vf
vi = 14.02 - vf
from the conservation of energy
113*vi^2 = 821*1.93^2 + 113*vf^2
113*(14.02- vf)^2 = 821*1.93^2 2 + 113*vf^2
vf= 5.07 m/s is the velocity after collision
Vi = 14.02 - 5.07
Vi = 8.95 m/s is the velocity before collison