Week 8 SPEED, VELOCITY AND ACCELERATION.pdf

Class presentation

1. YEAR 10 PHYSICS –SPEED, VELOCITY AND
ACCELERATION

2. 1. What is friction?
2. State two types of friction?
3. The diagram below illustrates a body of mass
10.0kg, being pulled by a horizontal force F. if
the body accelerates at 5.0ms
-2
and a frictional
force of 10N.
.
2
STARTER ACTIVITY
calculate the:
(i) Net force on it
(ii) Magnitude of F
(iii) Coefficient of kinetic friction.
[ g= 10ms
-2
]

3. LESSON OBJECTIVE(S) 3
TOPIC: SPEED, VELOCITY AND ACCELERATION.
LESSON OBJECTIVES
At the end of this lesson, students should be able
to:-
1. Define distance and state its SI unit?
2. Define displacement and state its SI unit?
3. Define speed and average speed.
4. Define velocity and average velocity.
5. Define acceleration and retardation.
6. Solve questions relating to speed, velocity and
acceleration.
KEY WORDS
i. Distance
ii. Displacement
iii. Speed
iv. Average speed
v. Acceleration
vi. Deceleration

4. Distance and Displacement
4
DISTANCE
•Distance is the difference or interval between one
position and another.
•Distance could be along a straight path, or a circular
path.
•The S.I unit of distance is metre(m).
•Examples of distance are: 20km, 5km, 60m 40m etc.

5. Distance and Displacement
5
DISPLACEMENT
•Displacement is defined
as distance traveled in a
specified direction.
•Examples of
displacement are:

6. Speed and Velocity
6
SPEED
•Speed is defined as the time rate of change of distance.
•It is distance travelled per unit time.
Speed =
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�??????��
??????=
�
�
s = distance covered
t = time taken to cover the distance
•The S.I unit of speed is metreper second (ms
-1
)

7. Speed and Velocity
7
Uniform speed or constant speed
•A body is said to undergo uniform speed when its time
rate of change of distance is constant.
•That is, when it covers equal distances in equal time
interval.
•e.gA body starts from rest and cover 5m after 2s, 10m
after 4s, 15m after 6s.

8. Speed and Velocity
8
VELOCITY
•Velocity is defined as the time rate of change of
displacement.
•It is displacement per unit time.
Velocity =
distance
time
V =
s
t
•Where v is velocity , s is displacement, t is time.
•The S.I unit of velocity is metreper second (ms
-1
)

9. Speed and Velocity
9
Uniform velocity or constant velocity
•A body is said to undergo uniform velocity when its time
rate of change of displacement is constant.
•That is, the body displaces equal amounts in equal time
interval.
•e.gA body starts from rest and displaces 7m after 3s,
14m after 6s, 21m after 9s.

10. Acceleration and Retardation
10
Acceleration
•Acceleration is the time rate of increase in velocity. It is increase in velocity per unit
time.
Acceleration =
increaseinvelocity
timetakefortheincrease
Acceleration =
finalvelocity−initialvelocity
time
•Given that acceleration = a , final velocity = v, Initial velocity = u, time = t
a =
v−u
t
•The S.I unit of acceleration is ms
-2

11. Acceleration and Retardation
11
Retardation
•Retardation is the time rate of decrease in velocity.
•Retardation is negative acceleration.
•It is also called deceleration.
Uniform acceleration
•A body is said to undergo uniform acceleration when the time rate of increase
in velocity is constant.
•That is, the velocity increases by equal amounts in equal time intervals.
•E.gA body starts from rest and its velocity becomes 5ms
-1
after 2s, 10ms
-1
after
4s, 15ms
-1
after 6s.

12. Example 1
12
What is the distance covered by a car
which travels with a constant speed of
20.8ms
-1
for 30s?
A.225.0mB. 450.5mC. 624.0m
D. 726.0mE. 834.5m

13. Solution to Example 1
13
Speed = 20.8ms
-1
; Time = 30s; Distance =?
Speed =
distance
time
∴Distance = speed ×time
= 20.8 ×30
= 624mC

14. Class Activity 1
14

15. Class Activity 2
15

16. Class Activity 3
16

17. Class Activity 4
17

18. Class Activity 5
18

19. Class Activity 6
19

20. Assignment