Everything Science Grade 10

CHAPTER 21. MOTION IN ONE DIMENSION 21.6

2. How can you tell by looking at the “Distance vs. Time” graph if the velocity

is constant?

3. How would the “Distance vs. Time” graph look for a car with a faster velocity?

4. How would the “Distance vs. Time” graph look for a car with a slower veloc-

ity?

Motion at constant acceleration ESAHD

The final situation we will be studying is motion atconstant acceleration. We know that
acceleration is the rate of change of velocity. So, if we have a constant acceleration, this
means that the velocity changes at a constant rate.

Let’s look at our first example of Vivian waiting at the taxi stop again. A taxi arrived and
Vivian got in. The taxi stopped at the stop street and then accelerated in the positive
direction as follows: After 1 s the taxi covered a distance of 2 , 5 m, after 2 s it covered
10 m, after 3 s it covered 22 , 5 m and after 4 s it covered 40 m. The taxi is covering a larger
distance every second. This means that it is accelerating.

2,5 m 10 m 22,5 m 40 m

t = 1 s t = 2 s t = 3 s t = 4 s

STOP

To calculate the velocity of the taxi you need to calculate the gradient of the line at each
second:

~v 1 s=∆∆~xt

=~xtf−~xi

f−ti

= 15 , 5 ms−− 00 ,m 5 s

= 5m·s−^1

Physics: Mechanics 413