If a strip of lightly cross-linked natural rubber initially at room temperature is heated in an oven, it can be observed to expand. If the same piece of rubber is stretched at room temperature to twice its original longitudinal dimensions then placed in the same oven, it can be observed to contract. How do you explain these phenomena

Aboxcar traveling at 12 m/s approaches a string of 5 identical boxcars sitting stationary on the track. the moving boxcar collides and links with the stationary cars and they all move off together along the track. what is the final speed of the cars immediately after the collision? (you may take the mass of each boxcar to be 18,537 kg.)

Aball is thrown horizontally from a cliff at 8m/s .in what direction is the ball moving 2s later?

In a game of pool, ball a is moving with a velocity v0 of magnitude v0 = 15 ft/s when it strikes balls b and c, which are at rest and aligned as shown. knowing that after the collision the three balls move in the directions indicated and assuming frictionless surfaces and perfectly elastic impact (that is, conservation of energy), determine the magnitudes of the velocities va, vb, and vc.