Question: The acceleration of a cart down a plane inclined at an angle a to horizontal can be determined by measuring the change in speed of the cart at two points, seperated by a distance s, along the inclined plane. Suppose two photocells are fixed at the two points along the plane. Each photocell measures the time for the cart, which has a length L to pass it. Identify the important variables in this test. List any assumptions that you feel are intrinsic to such as test.