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Drop everything and read!
Warm-up
Use the textbook to define and add the
following words to your glossary:
Acceleration
Velocity-Time Graph
Newton’s Second Law
Inertia Review: Newton’s First Law
YouTube - Sid the Science Kid "Ignatz's Inertia"
Acceleration
•The rate at which velocity changes with
time is called acceleration
•Acceleration is a measure of how quickly
velocity is changing.
•If velocity does not change, there is no
acceleration.
What does acceleration mean?
We often refer to acceleration as speeding
up BUT it really means any change in
velocity.
Ex. A driver slowing down to stop at a light
is accelerating.
Acceleration is a Vector
•Like velocity, acceleration is also a vector,
which means it has both size and direction.
•The direction of acceleration determines
whether an object will slow down, speed
up, or turn.
•We can have:
•Acceleration in the same direction as
motion=speed increases
•Acceleration in the opposite direction of
motion=speed decreases (negative
acceleration)
•Acceleration at a right angle to
motion=direction of motion changes
Calculating Acceleration
To calculate acceleration, you need to know
the starting velocity, the ending velocity, and
the time interval which the object changed.
Acceleration= (final velocity-initial velocity)
time
The standard unit for acceleration is meters
per second per second which is written as m/s2
(meters per second squared)
Let’s Practice
Ama starts sliding with a velocity of 1 m/s. After 3s,
her velocity is 7 m/s. What is Ama’s acceleration?
What do you know? Initial velocity=1m/s, final
velocity=7m/s, time=3s
Write the formula: a= v(final)-(V)initial
t
Substitute into the formula: a=7m/s-1m/s
3s
Calculate: 6m/s = 2m/s2
3s
You try!
A man walking at 0.5 m/s accelerates
to a velocity of 0.6m/s in 1s. What is his
acceleration?
You try!
A train traveling at 10m/s slows down
to a complete stop in 20s. What is the
acceleration of the train?
Velocity-Time Graphs
Acceleration, like position and velocity, can
change with time.
On a velocity-time graph:
1) A rising line on the velocity-time graph
shows positive acceleration (speeding up)
2)A flat line shows no acceleration
3) A falling line shows negative acceleration
(slowing down)
Newton’s Second Law of Motion
The acceleration of an object increases with
increased force and decreases with increased
mass.
IN SIMPLE TERMS: The harder you push, the
further it goes. The more mass the object has, the
harder it is to move it!