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Prepared by:
SITI FAIRUZ BINTI MOHD NOORL 20091002852
Acceleration & Deceleration
Previous Lesson…
Velocity
Displacement Distance
Speed
in a linear motion is the magnitude of
is the rate of change of
is the rate of change of
In a specified direction has the shortest magnitude of
Video…….
At the end of this lesson, student should be able to:- Define acceleration and
deceleration- State that a= v-u
t- Calculate acceleration and
deceleration.
Learning Outcome
60 kmh-1 100 kmh-1
Initial velocity , u = 60 kmh-1
Final Velocity , v = 100 kmh-1
Time, t = 5 s
What can you say about the velocity of the car?
Suppose the car was moving with an initial velocity of 12 ms-1 and takes 6s to stop.
Calculate its acceleration.
u = 12 ms-1
v = 0 ms-1
t = 6 s
a = v - u = -2 ms-2
t
So, we can say that the car accelerates at -2 ms-2 or
the car decelerates at 2 ms-2 .
How does acceleration relate to change of
velocity?
How does acceleration relate to change of
time?
What is acceleration?
Acceleration = Change in velocity
Time taken for the change
The car accelerates from an initial velocity, u, to a final velocity, v, in time, t.
The acceleration of the car is
a = v-u ms-1
t sVector quantitySI unit : ms-2
a positive
v positive
a negative
v negative
a negative
v positive
Direction of motion
Direction of motion
Direction of motion
Direction of motiona positive
v negative
Slows
down
Slows
down
Speeds
up
Speeds
up
We can analyse linear motion in a laboratory using a ticker timer
A
B
C
Direction of motion
What can you say about the velocity and
acceleration of the trolley in each case?
Distance between dots is the same. The trolley is moving with constant
velocity.
ADirection of motion
The distance between dots is increasing.The trolley is moving with increasing
velocity.It has a positive acceleration.Speeds up.
BDirection of motion
The distance between dots is decreasing.The trolley is moving with decreasing
velocity.It is decelerating.Slows down.
CDirection of motion
A sprinter runs from the starting line and achieves a velocity of 18ms-1 in 3s.
Calculate his acceleration.
Answer:
We know that:
u= 0ms-1 a = v-u
v= 18ms-1 t
t=3s = 18 - 0 ms-1
3 s
= 6 ms-2
A stationary car achieves a velocity of 40ms-1 in 10 seconds.
Calculate the acceleration of the car.
(Assume that the acceleration of the car is uniform throughout the journey).
Problem to solve…
Acceleration = Change of velocity
Time
= Final velocity – Initial Velocity
Time
= 40ms-1 – 0ms-1
10s
= 4ms-1
Answer..
At the end of this lesson, student should be able to:- Define acceleration and
deceleration- State that a= v-u
t- Calculate acceleration and
deceleration.
Learning outcome…
Read “Analysing Motion Graph”- (text book; page 28)
Do review questions (Exercise Book, page 107)
Homework….