2013 PHYS1131 Final

3

Question 1 (Marks: 20)

On a straight, flat section of road, a car follows a truck. Initially (t < 0), both are travelling at speed v0 = 90 k.p.h. The truck maintains constant speed throughout. The car is initially 2.0 seconds behind the truck, i.e. for t < 0 the car passes a given point on the road two seconds later than the truck. At some point, which we will call x=0, t=0, the car begins accelerating forwards at

a = 2.0 ms-­‐2. The car subsequently overtakes the truck and when the car is 50 metres ahead of the truck (at time t1), the car driver realises he is over the legal speed limit, so decelerates at 2.0 ms-­‐2.

When the car has slowed down to 90 k.p.h. (at time t2), it then maintains that constant speed.

(i)

Draw a clear, well-­‐labelled displacement-­‐time graph for the car and the truck for all t and x relevant to this question (i.e. include t < 0 and t > t2).

The car and truck should be illustrated in the same figure. Do not draw them on two separate figures.

Ensure that the time axis is horizontal and the displacement axis is vertical.