1. AccelerationAcceleration
September 18, 2013September 18, 2013

2. ObjectivesObjectives
1.1. Calculate accelerationCalculate acceleration
2.2. Describe acceleration on a Speed vs.Describe acceleration on a Speed vs.
Time graphTime graph

3. AccelerationAcceleration
 Galileo developed this idea as wellGalileo developed this idea as well
 Found that balls rolling down an inclineFound that balls rolling down an incline
rolled faster and fasterrolled faster and faster

4. CalculationCalculation
 Acceleration =Acceleration = Change in velocityChange in velocity
timetime
 Change in velocity = VChange in velocity = VFF - V- VII

5. THEREFORETHEREFORE
 Acceleration is a change in:Acceleration is a change in:
– SpeedSpeed
– DirectionDirection
– Both speed and directionBoth speed and direction
 A body undergoes acceleration when thereA body undergoes acceleration when there
is a change in its state of motionis a change in its state of motion

6. Suppose we are drivingSuppose we are driving
 In 2 second we steadily increase ourIn 2 second we steadily increase our
velocity from 30 meters per second 40velocity from 30 meters per second 40
meters per second.meters per second.
 Change of velocity is 5 meters per secondChange of velocity is 5 meters per second
in each secondin each second
 Acceleration = 5 m/sAcceleration = 5 m/s22

7.  A snail accelerates from 2 m/s to 4 m/s in 2A snail accelerates from 2 m/s to 4 m/s in 2
seconds. What is the snail’s averageseconds. What is the snail’s average
acceleration?acceleration?

8. ForcesForces
September 20, 2013September 20, 2013

9. ObjectivesObjectives
1.1. Explain the difference between BalanceExplain the difference between Balance
and Unbalance Forcesand Unbalance Forces
2.2. Describe and calculate the relationshipDescribe and calculate the relationship
between mass, acceleration, and Forcebetween mass, acceleration, and Force

10. Net ForceNet Force
 Objects don’t speed up, slow down, orObjects don’t speed up, slow down, or
change direction without forcechange direction without force
 Net Force - All the forces taken to changeNet Force - All the forces taken to change
the motion of the objectthe motion of the object

11. Applied Force Net ForceApplied Force Net Force
 5 N5 N
 5 N5 N
5 N5 N   5 N5 N
5 N5 N   10 N10 N
10 N10 N
0 N (balanced force)0 N (balanced force)
 5 N5 N

12. Balanced ForceBalanced Force
 When the force on anWhen the force on an
object are equal in sizeobject are equal in size
and opposite directionand opposite direction
 Results in the objectResults in the object
not moving (The forcesnot moving (The forces
cancel each other out)cancel each other out)

13. Balanced vs. UnbalancedBalanced vs. Unbalanced
 Only when forces are unbalanced can anOnly when forces are unbalanced can an
object be set into motionobject be set into motion

15. Force and AccelerationForce and Acceleration
 Any object that accelerates depends on aAny object that accelerates depends on a
force to make it accelerateforce to make it accelerate
 What is the force in a free fall?What is the force in a free fall?
 Acceleration ~ Net ForceAcceleration ~ Net Force

16.  If you push on a shopping cart it willIf you push on a shopping cart it will
accelerate. If you apply four times the netaccelerate. If you apply four times the net
force, how much greater will theforce, how much greater will the
acceleration be?acceleration be?
 If the net force acting on a sports car isIf the net force acting on a sports car is
increased by five, how much greater willincreased by five, how much greater will
the acceleration be?the acceleration be?

17. Free FallFree Fall
 When air resistance doesn’t affect theWhen air resistance doesn’t affect the
motion of a falling objectmotion of a falling object
 Free falling objects gain speed at the rate ofFree falling objects gain speed at the rate of
9.8 m/s every second9.8 m/s every second
 9.8 m/s9.8 m/s22

18. GravityGravity
 Objects in free fall gain speed because ofObjects in free fall gain speed because of
gravitygravity
 Gravity is 9.8 m/sGravity is 9.8 m/s22
 What about if you throw an object up?What about if you throw an object up?

19. Mass and InertiaMass and Inertia
 The more massive theThe more massive the
more Inertiamore Inertia
 The more FORCEThe more FORCE
neededneeded
OROR
 The less accelerationThe less acceleration

20. RememberRemember
 Mass is not WeightMass is not Weight
 Mass is not volumeMass is not volume
 Mass is the amount ofMass is the amount of
matter in an objectmatter in an object

21. Weight is ForceWeight is Force
 Force due to gravity that act’s on an object’sForce due to gravity that act’s on an object’s
massmass
 Mass doesn’t change, weight can (Moon vs.Mass doesn’t change, weight can (Moon vs.
Earth)Earth)
 Mass is proportional to WeightMass is proportional to Weight

22. NewtonNewton
 Standard unit ofStandard unit of
Weight/ForceWeight/Force
 Symbol – NSymbol – N
 F = maF = ma
 One kilogram WeighsOne kilogram Weighs
9.8 Newtons9.8 Newtons