What is the interval in which the cart is moving forward at constant speed?
The displacement-time graph below represents the motion of a cart initially moving forward along a straight line. 

The answer is 3. The interval in which the cart is moving forward at constant speed is BC. This question has to do with graphine motion and time displacement. Graphing motion is very important in physics. Physics is the scientific study of matter and the way it moves throughout time and space.

Physics is important because it allows us to study and understand ourselves and our surroundings better. Physics can help us accurately estimate if a comet will hit the earth, how far a car will be able to stop, and even explain why gravity exists and how we can alter it.