CHAPTER 2
SPEED, VELOCITY AND ACCELERATION
Displacement
Displacement is defined as the distance travelled along a particular direction.
(Displacement is a vector quantity.)
distance travelled
Starting point
Finishing point
displacement
3m
100 m
20 m
4m
distance travelled = 100 + 20 = 120 m
displacement = 80 m
distance travelled =
displacement =
4+3 = 7m
5m
Velocity
Velocity is defined as the rate of change of displacement. ( Velocity is a vector quantity. )
Speed
Average velocity
Speed is defined as the rate of change of distance. ( Speed is a scalar quantity. )
Average velocity is defined as the ratio of the total displacement to the time taken
to travel that displacement.
v =
d
t
( v = speed, d = distance, t = time taken )
= ms-1
= cms-1
= fts-1
= ms-1
Acceleration
Acceleration is defined as the rate of change of velocity.
= ms-2
= cms-2
= fts-2
= ms-2
distance – time graph
distance ( m )
40
30
20
20 m
10
2s
0
0
1
2
3
Slope of ( distance – time ) graph =
Uniform motion ( Motion with constant velocity is called uniform motion. )
=
0s
1s
d=0m
10 m
20 m
2s
4
time ( s )
= 10 m / s
speed
2s
3s
4s
20 m
30 m
40 m
Accelerated motion ( Motion with changing velocity is called accelerated motion. )
t=0s
1s
2s
3s
4s
d=0m
1m
4m
9m
16 m
distance ( m )
distance – time graph
16
9
Slope of ( distance – time ) graph at ( t = 2 s ) =
6m
4
=
1.5 s
1
0
0
1
2
3
4
time ( s )
6m
1.5 s
= 4m/s
speed at ( t = 2 s )
Slope of the speed – time graph
=
acceleration
Exercises
11.
12.
13.
14.
2019 MAY / JUNE 42
Distance = ……………………………… [ 3 ]
15.
2020 MARCH 42
Fig. 1.1
21.
2020 M/J 42
Time / min
Fig. 1.1