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What is Acceleration
It is the rate of change in velocity over time
Formula for Acceleration
Acceleration = Change in Velocity/Time Taken
Acceleration = (Final Velocity - Initial Velocity)/Time Taken
a = (v - u)/t
where
v = Final Velocity
u = Initial Velocity
t = time taken
What is Unit of Measurement of Acceleration
it is m/s
2
(We know that formula for velocity is m/s.because we again divide it by s,Measure becomes m/s
2
Example 1
A car is moving at a speed of 6 meters/Second
In 5 Seconds, he increases its speed to 16 meters /second
What is Acceleration
Initial Velocity = u = 6
Final Velocity = v = 16
Time Taken = t = 5
Acceleration=Increase in Velocity/Time Taken
a = (Final Velocity - Old Velocity)/Time Taken
a = (v - u)/t
a = (16 - 6)/5
a = (10)/5
a = 2 Meters/Second 2
Example 2
A car Is stationary
In 5 Seconds,it reaches its speed to 16 meters /second
What is Acceleration
Because,Car is Stationary,Its initial velocity = 0
So u = 0
V = 16
Acceleration = Increase in Velocity/Time Taken
a = (Final Velocity - Old Velocity)/Time Taken
a = (v - u)/t
a = (16 - 0)/5
a = (16)/5
a = 3.2 Meters/Second 2
Negative Acceleration
Sometimes,acceleration of a body decreases
Example
Speed of car decreases
This is called negative acceleration or Retardation
Example 3
A car is running at a speed of 30 meters/second
It applies brake and reaches speed of 22 meters per second in 2 Seconds
What is acceleration
Initial Velocity = u = 30
Final Velocity = v = 22
Time Taken = t = 2
Acceleration=Increase in Velocity/Time Taken
a = (Final Velocity - Old Velocity)/Time Taken
a = (v - u)/t
a = (22 - 30)/2
a = -8/2
a = -4 Meters/Second 2
So in this case,there is Acceleration of -4 Meters/Second 2
We can say that there is Negative Acceleration of 4 Meters/Second 2
Note
Negative Acceleration or Retardation of 4 Meters/Second 2
Note: Negative Acceleration is also called retardation
Questions
Q 1 Page 103 -
When will you say a body is in
(i) uniform acceleration? (ii) nonuniform acceleration?
Q 2 Page 103 - A bus decreases its speed from 80 km h–1 to 60 km h–1 in 5 s. Find the acceleration of the bus.
Q 3 Page 103 - A train starting from a railway station and moving with uniform acceleration attains a speed 40 km h–1 in 10 minutes. Find its acceleration
NCERT Question 9 - State which of the following situations are possible and give an example for each of these:
Example 8.4 - Starting from a stationary position, Rahul paddles his bicycle to attain a velocity of 6 m s–1 in 30 s. Then he applies brakes such that the velocity of the bicycle comes down to 4 m s-1 in the next 5 s. Calculate the acceleration of the bicycle in both the cases.
