Page 175 - Physics

Linear motion

Displacement ( ) s Total time is;
Veloc ity ( ) v = Time ( ) t
s  4 s 3 s
v =
t = 7 s
u v
= + Total distance travelled
2 Average speed= Total time taken
Where, u is the initial velocity, and v v = s
is the fi nal velocity. t

The SI unit for the magnitude of average = 32 m
velocity is the same as the units for 7 s
average speed, that is metre per second v = 4.57 m/s
(m/s). Therefore, its average speed was

Note: Velocity at a particular instant is 4.57 m/s
called instantaneous velocity. A body is Average velocity: To fi nd the
said to move with uniform velocity if its average velocity we need to consider
rate of change of displacement with time
is constant. the magnitude and direction of the
displacement.

Example 8.2 Total Displacement:
Total displacement = displacement to
An object travelled a distance of 20 m the right + displacement to the left.
to the right in 4 s and then 12 m to the
left in 3 s. For its total motion, what = 20 m + (-12) m
was its average speed and its average = 8 m
velocity? The displacement is 8 m to the right.
Total time,
Solution
t = 4s + 3s
When the object is moving to the = 7 s

right, its displacement is positive and Average velocity,
when moving to the left it is negative. s
Time is always positive. v =
t
Average speed: 8 m
=
The total distance travelled is; 7 s

s = 20 m + 12 m = 1.14 m/s

= 32 m Therefore, its average velocity was
1.14 m/s to the right.

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Physics Form 1 Final.indd 169 16/10/2024 20:58