What type of wave is produced when you move one end of a horizontal spring up and down

If a balloon is taken outside on a very cold day, what will occur?

If an athlete runs once around a track, back to the starting line, her average velocity is zero. true or false?

Consider a system with two masses that are moving away from each other. why will the kinetic energy differ if the frame of reference is a stationary observer or one of the masses?