Question

4. The velocity-time graph (v-t) of a car moving along a
level road is shown below. The average speed of the
car in the time interval 0 to 8 s is about
v (ms ) –1
10
t (s)
–5
5 8 0
(1) 3.33 ms–1 (2) 1.20 ms–1
(3) 4.48 ms–1 (4) 8.43 ms–1

Answer 1

Given:

The velocity-time graph (v-t) of a car moving along a level road is shown.

To find:

The average speed of the car in the time interval 0 to 8 s is about v (ms ) –1

Solution:

From given, we have,

The velocity-time graph (v-t) of a car moving along a level road is shown.

Average speed = total distance / total time

The point at which the line intersects the x-axis is,

10/x = 5/5-x

x = 10/3 s

Area of triangle 1 = 1/2 × 10/3 × 10 = 100/6 m²

Area of triangle 2 = 1/2 × 5/3 × 5 = 25/6 m²

Area of rectangle = 5 × 3 = 15 m²

Total area = 100/6 + 25/6 + 15 = 215/6 m²

Average speed = 215/(6 × 8) = 4.479 m/s

The average speed of the car in the time interval 0 to 8 s is about (3) 4.48 ms–1.