Definition: Acceleration
 Vector quantity:
magnitude (value) & direction
 Rate at which an object changes its velocity.
 “How fast an object is getting faster”
If the velocity of an
object is changing, it is
accelerating!
Definition: Acceleration
 “How fast an object is getting faster”
 Every second,
object goes 10 m/s faster
to the north
 Units are:
 Meters per second per second
 m/s/s
Equation: Acceleration
 𝑎𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛 =
a =
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑡𝑖𝑚𝑒
∆𝑣
∆𝑡
=
𝑣𝑓𝑖𝑛𝑎𝑙 −𝑣𝑖𝑛𝑖𝑡𝑖𝑎𝑙
𝑡𝑓𝑖𝑛𝑎𝑙 −𝑡𝑖𝑛𝑖𝑡𝑖𝑎𝑙
Animation: Acceleration
 Physics Classroom: Acceleration Animation
Constant Acceleration
 Velocity changes by a constant amount each second.
 The magnitude can change. (How fast it is going)
 And/or…. The direction can change.
 An object with a constant velocity is not accelerating.
 In this class, ALL acceleration will be constant.
Accelerating Objects Are
Changing Their Velocity
Equation: Acceleration
 𝑎𝑐𝑐𝑒𝑙𝑒𝑟𝑎𝑡𝑖𝑜𝑛 =
=
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦
𝑐ℎ𝑎𝑛𝑔𝑒 𝑖𝑛 𝑡𝑖𝑚𝑒
∆𝑣
∆𝑡
=
𝑣𝑓𝑖𝑛𝑎𝑙 −𝑣𝑖𝑛𝑖𝑡𝑖𝑎𝑙
𝑡𝑓𝑖𝑛𝑎𝑙 −𝑡𝑖𝑛𝑖𝑡𝑖𝑎𝑙
 A car goes from 0 m/s to 40 m/s in 10 seconds.
What is the acceleration of the car?
𝑚
 Accel =
𝑣𝑓𝑖𝑛𝑎𝑙 −𝑣𝑖𝑛𝑖𝑡𝑖𝑎𝑙
𝑡𝑓𝑖𝑛𝑎𝑙 −𝑡𝑖𝑛𝑖𝑡𝑖𝑎𝑙
40𝑠𝑒𝑐 − 0 𝑚/𝑠𝑒𝑐
=
10 𝑠𝑒𝑐 −0 𝑠𝑒𝑐
=
40 𝑚/𝑠𝑒𝑐
10 𝑠𝑒𝑐
= 4 m/s /s
A car traveling at 60 mph accelerates to 90 mph
in 3 seconds. What is the car’s acceleration?
Acceleration
=
Velocity(final) - Velocity(original)
time
=
=
90 mph - 60 mph
3 seconds
30 mph
3 seconds
= 10 mph/second
Study in Acceleration
 Rocket Sled
Graphing: Acceleration
Position vs. Time
Slope of x vs. t
= velocity
Velocity vs. Time
Slope of v vs. t
= acceleration
Accel. vs. Time
Graphing: Acceleration
Change in Velocity
- Speed vs Time Graph:
Constant acceleration
produces a straight line
(linear slope, rise/run
a = v/t
Free fall
 The constant acceleration of
an object moving only under
the force of gravity (g).
 The acceleration caused by
gravity is 10 m/s2
 If there was no air, all objects
would fall at the same speed
 Doesn’t depend on mass
 After 1 second falling at 10 m/s
 After 2 seconds 20 m/s
 3 seconds 30 m/s
Falling
 Air resistance will
increase as it falls
faster
 An upward force on
the object
 Eventually gravity will
balance with air
resistance
 Reaches terminal
velocity - highest
speed reached by a
falling object.
Terminal velocity
 Force of gravity is constant
air resistance increases as
you speed up
 until the force is equal


Equal forces, no
acceleration

constant velocity
terminal velocity
Balloon Racers
 What will happen if I let go of the blown up balloon?
 Why did that happen?
 How can we measure the speed, distance or
acceleration of the balloon?
 A track?
 Attach the balloon to something?