A car starts from rest and accelerates to a speed of 60 mph in 20 s. The acceleration during this period is constant. For the next 20 minutes the car moves with the constant speed of 60 mph. At this time the driver of the car applies the brake and the car decelerates to a full stop in 10 s. The variation of the speed of the car with time is shown in the accompanying diagram. Determine the total distance traveled by the car and the average speed of the car over this distance. Also plot the acceleration of the car as a function of time.

Question

Answer 1

During the initial 20 seconds, the speed of the car increases linearly from a value of zero

to 60 mph. Therefore, the average speed of the car is 30 mph during this period. The

distance traveled during this period is



During the next 20 minutes the car moves with a constant speed of 60 mph and the

distance traveled during this period is



Because the car decelerates at a constant rate from a speed of 60 mph to 0, the average

speed of the car during the last 10 seconds is also 30 mph, and the distance traveled

during this period is



The total distance traveled by the car is



To plot the acceleration of the car as a function of time, first we need to compute the

acceleration during the first 20 seconds, the next 20 minutes, and the last 10 seconds.

During the initial 20 seconds, the acceleration of the car is



Note during this period, the speed of the car changes from 0 toV ? 60 mph ? 88 ft/s .

During the next 20 minutes the car moves with constant speed of 60 mph and therefore

acceleration is zero.

During the last 10 seconds the car decelerates at the following rate.