AccelerationAcceleration

Chapter 3 Section 1Chapter 3 Section 1

What is Acceleration?What is Acceleration?

Speed Speed is the rate of change of is the rate of change of position.position.

Galileo definedGalileo defined Acceleration Acceleration as the as the rate of change of velocity.rate of change of velocity.– What does that mean it has?What does that mean it has?

HINTHINT

Acceleration Hints!Acceleration Hints!Because velocity includes speed and Because velocity includes speed and direction of an object, acceleration direction of an object, acceleration can be a change in:can be a change in:– How fast the object is movingHow fast the object is moving– What direction the object is movingWhat direction the object is moving

Acceleration occurs when an object Acceleration occurs when an object changes its speed or direction, or changes its speed or direction, or both!both!

Speeding up or Slowing down?Speeding up or Slowing down?When a car speeds When a car speeds up, that is up, that is POSITIVE POSITIVE ACCELERATION!ACCELERATION!

When a car slows When a car slows down, that is down, that is NEGATIVE NEGATIVE ACCELERATION or ACCELERATION or DECELERATION!DECELERATION!

Acceleration FormulaAcceleration FormulaAcceleration = Change in Velocity/TimeAcceleration = Change in Velocity/Time

A = A = ΔΔV/TV/T

Positive AccelerationPositive Acceleration

A motorcycle starts at rest and A motorcycle starts at rest and accelerates to 80 m/s in 20 secondsaccelerates to 80 m/s in 20 secondsA= A= ΔΔV/T = 80 m/s/ 20sV/T = 80 m/s/ 20s

A= 4 m/sA= 4 m/s22

Distance vs. Time GraphDistance vs. Time GraphWhen AcceleratingWhen Accelerating

Negative Acceleration/DecelerationNegative Acceleration/DecelerationA skateboarder moves in a straight A skateboarder moves in a straight line at 3 m/s and comes to a stop in 2 line at 3 m/s and comes to a stop in 2 s.s.

A= A= ΔΔV/T =– 3 m/s/2sV/T =– 3 m/s/2s

A= -1.5 m/sA= -1.5 m/s22

Free FallFree Fall

When air resistance doesn’t affect When air resistance doesn’t affect the motion of a falling object, we say the motion of a falling object, we say the object is in free fall.the object is in free fall.

Downward falling objects gain speed Downward falling objects gain speed because of the force of gravity.because of the force of gravity.

Object thrown UpwardsObject thrown Upwards

What happens when an object gets What happens when an object gets thrown upwards?thrown upwards?– While going up, it moves against While going up, it moves against

gravity.gravity.– At the highest point, when it changes At the highest point, when it changes

direction from upward to downward, its direction from upward to downward, its instantaneous speed is zero.instantaneous speed is zero.

– Then it starts downward just as if it had Then it starts downward just as if it had been dropped from rest.been dropped from rest.

AccelerationAcceleration

Acceleration is the rate of change of Acceleration is the rate of change of velocity.velocity.

Acceleration = Acceleration = change in velocitychange in velocity

time intervaltime interval

Symbol: ASymbol: A

Units: m/sUnits: m/s22