An automated delivery cart travels at a constant initial speed UUU. The operator applies the brakes at time t=0t = 0t=0 and the cart comes to a stop at t=2.5 st = 2.5\text{ s}t=2.5 s.
The graph below shows the variation of the braking force FFF on the cart with time ttt.

Use Newton's second law of motion to explain the physical quantity represented by the area under the FFF-ttt graph.
The total mass of the cart is 50 kg50\text{ kg}50 kg. Use the graph to calculate the initial speed UUU.
Describe the shape of the speed-time graph of the cart from t=0t = 0t=0 to t=2.5 st = 2.5\text{ s}t=2.5 s. State the initial and final coordinates on this graph.