# Question 5

The track for a motorbike race consists of a straight, horizontal section that is 800 m long.

A participant, such as the one in the picture above, rides at a certain average speed and completes the 800 m course in 75 s. To maintain this speed, a constant driving force of 240 N acts on the motorbike.

5.1 Calculate the average power developed by the motorbike for this motion. (3)

Another person practices on the same motorbike on a track with an incline. Starting from rest, the person rides a distance of 450 m up the incline which has a vertical height of 5 m, as shown below.

The total frictional force acting on the motorbike is 294 N. The combined mass of rider and motorbike is 300 kg. The average driving force on the motorbike as it moves up the incline is 350 N. Consider the motorbike and rider as a single system.

5.2 Draw a labelled free-body diagram for the motorbike-rider system on the incline. (4)

5.3 State the WORK-ENERGY theorem in words. (2)

5.4 Use energy principles to calculate the speed of the motorbike at the end of the 450 m ride. (6)

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