Question

The speed-time graph for a car is shown in the following figure:

1. Find how far the car travels in the first 4 seconds. Shade the area on the graph that represents the distance travelled by the car during the period.
2. Which part of the graph represents uniform motion of the car?

Answer 1

The motion during the first 4 seconds is not uniformly accelerated. So, the distance travelled by car in the first 4 seconds is calculated using the graphical method.

(a) Number of squares in the shaded part of the graph is 320.5

One small square m x-axis represents `t = 2/5 s` 

One small square on the y-axis represents.

`v = 2/3  ms^-1`

∴ area of each square, `v xx t`

= `2/3 xx 2/5`

= `4/15 m`

Total area = `61.5 × 4/15`

= 16.4 m

(b) The limiting flat portion of the curve describes the constant speed of the car, i.e., a speed of 6.0 m s⁻¹. At this stage, the acceleration of the car is zero.

Therefore, a portion of the graph between t = 6 s to 10 s, describes the uniform motion of the car.