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Acceleration
Chapter 3 Section 1
What is Acceleration?
Speed is the rate of change of
position.
Galileo defined Acceleration as the
rate of change of velocity.
– What does that mean it has?
HINT
Acceleration Hints!
Because velocity includes speed and
direction of an object, acceleration
can be a change in:
– How fast the object is moving
– What direction the object is moving
Acceleration occurs when an object
changes its speed or direction, or
both!
Speeding up or Slowing down?
When a car speeds
up, that is
POSITIVE
ACCELERATION!
When a car slows
down, that is
NEGATIVE
ACCELERATION or
DECELERATION!
Acceleration Formula
Acceleration = Change in Velocity/Time
A = ΔV/T
Positive Acceleration
A motorcycle starts at rest and
accelerates to 80 m/s in 20 seconds
A= ΔV/T = 80 m/s/ 20s
A= 4 m/s2
Distance vs. Time Graph
When Accelerating
Negative Acceleration/Deceleration
A skateboarder moves in a straight
line at 3 m/s and comes to a stop in
2 s.
A= ΔV/T =– 3 m/s/2s
A= -1.5 m/s2
Free Fall
When air resistance doesn’t affect
the motion of a falling object, we say
the object is in free fall.
Downward falling objects gain speed
because of the force of gravity.
Object thrown Upwards
What happens when an object gets
thrown upwards?
– While going up, it moves against
gravity.
– At the highest point, when it changes
direction from upward to downward, its
instantaneous speed is zero.
– Then it starts downward just as if it had
been dropped from rest.
Acceleration
Acceleration is the rate of change of
velocity.
Acceleration = change in velocity
time interval
Symbol: A
Units: m/s2