Now that I think of it, there's only 1 experiment that I think would be worth adding onto the list which is investigating collisions.
You would set up your ramp, video analysis device (a video recorder and software that enables you to view the footage of the video frame by frame) and ruler beneath your ramp as it flattens off against a wall. You would record, let go of the trolley and keep recording until the trolley reaches the bottom of the ramp, collides with the wall and comes to rest. Then measure the mass of the trolley. Stop recording and view the recording frame by frame, picking out a point of reference on the ruler and counting the number of frames taken by the trolley to pass that point. You can work out time using:
Time= Number of frames taken * (1/ frame rate of camera)
Using the calculated time and the measured length, you can work out the velocity of the toy car using:
Velocity = Length/ time
Using this procedure, you can see how the velocity of the trolley varies before and after colliding with the wall.