Ramps are often used in conjunction with trolleys to investigate acceleration, speed or as a runway or platform for various experiments.
Ramps can be constructed fairly easily from sheets of plywood with raised wooden edges to keep the trolleys on the ramp. They may be any length although for acceleration experiments in particular, the longer the ramp is, the better. A sensible length is probably around 1.5m with a good width being about twice the width of a trolley.
If narrow trolleys are to be used, wide guttering with a flat bottom may be used. This plastic guttering can easily be cut to the desired length, is lightweight and fairly robust.
Wooden ramps should not be made to be too heavy, firstly because they may need to be moved from class to class by the technician but also because students may need to move them around. Ensure all edges are sanded smooth to reduce the risks of splinters.