Page 126 - SCERT Kerala State Syllabus 8th Standard Basic Science Textbooks English Medium Part 1_Neat

A body has uniform velocity if it covers equal displacements in
the same direction in equal intervals of time.

If either speed or direction changes, the velocity is non
uniform.

Complete Table 9.9 based on the above information.
Uniform Non uniform Reason
velocity velocity

Car A Neither the magnitude nor the
direction changes.

Car B
Car C Magnitude of velocity does not
change. Direction changes.

Table 9.9
You might have learned to distinguish between uniform velocity and
non uniform velocity. Now find out examples for bodies travelling in
uniform as well as non uniform velocity and write them down.

Uniform velocity
when light travels through vacuum

Non uniform velocity
a train starting and moving out of the station

Fig. 9.10
Acceleration

Imagine that you are sitting inside a car. The velocity of the car keeps
on changing when it starts and moves forward along a straight line
path. How does the driver manage this? Observe the Fig. 9.10 showing
the use of a device used for bringing about change in velocity, namely
the accelerator.
Details of the journey of a car in a straight line are given as a line
diagram in Fig 9.11. Analyse the information and complete Table 9.10.

0 m/s 5 m/s 10 m/s 10 m/s 6 m/s 0 m/s
A B C D E F
0 5 s 10 s 15 s 20 s 25 s
Fig. 9.11

Basic Science VIII 125