The graph on the right shows the speed of a vehicle over time.

a) During what time interval was the acceleration zero?

On a speed-time graph any horizontal line represents constant speed. In this section no acceleration takes place. The time period 6-11 hours indicates zero acceleration.

b) What is the greatest speed reached by the vehicle?

110km/hr

c) What is the acceleration of the vehicle during the first two hours?

Acceleration is the rate of change of .the speed of the vehicle over time. The gradient of the speed-time graph is therefore the acceleration.
Over the first two hours the speed goes from 0 to 30km/hr. The gradient and therefore the acceleration is 30km/hr/2/hr = 15km/hr/hr

d) What is the greatest acceleration reached by the vehicle during its journey.

The steepest slope in the speed-time graph gives us the maximum acceleration of the vehicle. The steepest part of the graph is during between 5 and 6 hours where the speed increases from 50km/hr to 110km/hr.

The acceleration is 60km/hr/1hr = 60km/hr/hr

e) What is the magnitude of the deceleration of the vehicle?

The steepest negative slope on the graph is the maximum deceleration. This occurs during the time between 11-12 hours. The speed decreases from 110 to 0 km/hr in hour. So the deceleration is 110km/hr/hr.

The graph on the right shows the speed of a vehicle over time.

a) During what time interval was the acceleration zero?

Between 8 and 11 hours.

b) What is the greatest speed reached by the vehicle?

150km/hr

c) What is the acceleration of the vehicle during the last hour of the journey?

76km/hr/1hr = 76km/hr/hr

d) What is the greatest acceleration reached by the vehicle during its journey.

76km/hr/hr

e) Describe the motion of the vehicle during the first 8 hours of its journey.

The vehicle's acceleration is slowly decreasing as it approaches a constant speed of 74km/hr