An object travels in a circular orbit. If the speed of the object is doubled, what happens to its centripetal acceleration?

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.)

How do you know how many valence electrons an atom has?

Does current flow through or across a resistor?