A 70 kg student stands on top of a 5.0 m platform diving board . how much gravitational potential energy does the student have? how much work did it take for the student to travel from the ground to the top of the platform diving board?

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.)

Ineed the answer to question 1 , i’m desperate

At very high pressures, gases become and will eventually a) more dense; become hotter b) more dense; change to a liquid or solid c) less dense; combust d) less dense; turn into a liquid