Everything Science Grade 10

CHAPTER 21. MOTION IN ONE DIMENSION 21.6

Vivian’s velocity is:

v=∆∆~xt

=xtf−xi

f−ti

=^100100 ms−−^00 sm

= 1m·s−^1

Vivian’s velocity is 1 m·s−^1. This means that she walked 1 m in the first second, another
metre in the second second, and another in the third second, and so on. For example, after
50 s she will be 50 m from home. Her position increases by 1 m every 1 s. A diagram of
Vivian’s position is shown below:

b

x= 100 m

t = 0 s t = 50 s t = 100 s

x= 0 m x= 50 m

b b

We can now draw graphs of position vs.time (~xvs.t), velocity vs. time (~vvs.t) and ac-
celeration vs.time (~avs.t) for Vivian moving at a constant velocity. The graphs are shown
here:

0

20

40

60

80

100

0 20 40 60 80 100

position

x

(m)

timet(s)

b

∆t

b ∆x

b

0

1

2

0 20 40 60 80 100

velocity

v

(m

−·s

1 )

timet(s)

b b b

0

1

2

0 20 40 60 80 100

acceleration

a(m

−·s

2 )

timet(s)

b b b

Graphs for motion at constant velocity (a) position vs. time (b) velocity vs. time (c) accel-
eration vs. time. The area of the shaded portion in thevvs.tgraph corresponds to the
object’s displacement.

In the evening Vivian walks 100 m from the bus stop to her house in 100 s. Assume that
Vivian’s house is the origin. The following graphs can be drawn to describe the motion.

Physics: Mechanics 409