Everything Science Grade 10

21.6 CHAPTER 21. MOTION IN ONE DIMENSION

~v 2 s=∆∆~xt

=~xtf−~xi

f−ti

= 215 , 5 ms−− 15 , 5 ms

= 10m·s−^1

~v 3 s=∆∆~xt

=~xtf−~xi

f−ti

= 330 , 5 ms−− 215 , 5 ms

= 15m·s−^1

From these velocities, we can draw the velocity-time graph which forms a straight line.

The acceleration is the gradient of thevvs.tgraph and can be calculated as follows:

a=∆∆~vt

=~vtf−~vi

f−ti

=^15 m·s

− (^1) − 5 m·s− 1
3 s− 1 s
= 5m·s−^2
The acceleration does not change during the motion (the gradient stays constant). This is
motion at constant or uniform acceleration.
The graphs for this situation are shown below:
0
5
10
15
20
0 1 2 3 4
position
x
(m)
timet(s)
b
b
b
0
5
10
15
0 1 2 3 4
velocity
v
(m
−·s

1 )

timet(s)

b

b

b

0

1

2

3

4

5

6

7

8

9

0 1 2 3 4

acceleration

a

(m

−·s

2 )

timet(s)

bbb

Graphs for motion with a constant acceleration starting from rest.

414 Physics: Mechanics