Acceleration Acceleration

September 19, 2014September 19, 2014

ObjectivesObjectives

1.1. Calculate accelerationCalculate acceleration

2.2. Describe acceleration on a Speed vs. Time Describe acceleration on a Speed vs. Time graphgraph

Galileo and Galileo and MotionMotion

S = D/TS = D/T

Except for friction – objects Except for friction – objects fall at the same timefall at the same time

Force required to start an Force required to start an object, but not to keep it object, but not to keep it movingmoving

Force – Push or pullForce – Push or pull

Inertia – tendency of an object to Inertia – tendency of an object to resist any change in its motionresist any change in its motion

AccelerationAcceleration

Galileo developed this idea as wellGalileo developed this idea as well

Found that balls rolling down an incline Found that balls rolling down an incline rolled faster and fasterrolled faster and faster

CalculationCalculation

Acceleration = Acceleration = Change in velocityChange in velocity

timetime

Change in velocity = VChange in velocity = VFF - V - VII

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 there A body undergoes acceleration when there is a change in its state of motionis a change in its state of motion

Suppose we are drivingSuppose we are driving

In 2 second we steadily increase our In 2 second we steadily increase our velocity from 30 meters per second 40 velocity from 30 meters per second 40 meters per second.meters per second.

Change of velocity is 5 meters per second in Change of velocity is 5 meters per second in each secondeach second

Acceleration = 5 m/sAcceleration = 5 m/s22

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

ForcesForces

June 2, 2014June 2, 2014

ObjectivesObjectives

1.1. Explain the difference between Balance Explain the difference between Balance and Unbalance Forcesand Unbalance Forces

2.2. Describe and calculate the relationship Describe and calculate the relationship between mass, acceleration, and Forcebetween mass, acceleration, and Force

Net ForceNet Force

Objects don’t speed up, slow down, or Objects don’t speed up, slow down, or change direction without forcechange direction without force

Net Force - All the forces taken to change Net Force - All the forces taken to change the motion of the objectthe motion of the object

Applied Force Net ForceApplied Force Net Force

5 N5 N

5 N5 N

5 N 5 N 5 N 5 N

5 N 5 N 10 N 10 N

10 N10 N

0 N (balanced force)0 N (balanced force)

5 N5 N

Balanced ForceBalanced Force

When the force on an When the force on an object are equal in size object are equal in size and opposite directionand opposite direction

Results in the object Results in the object not moving (The forces not moving (The forces cancel each other out)cancel each other out)

Balanced vs. UnbalancedBalanced vs. Unbalanced

Only when forces are unbalanced can an Only when forces are unbalanced can an object be set into motionobject be set into motion

Force and AccelerationForce and Acceleration

Any object that accelerates depends on a Any 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

If you push on a shopping cart it will If you push on a shopping cart it will accelerate. If you apply four times the net accelerate. If you apply four times the net force, how much greater will the force, how much greater will the acceleration be?acceleration be?

If the net force acting on a sports car is If the net force acting on a sports car is increased by five, how much greater will increased by five, how much greater will the acceleration be?the acceleration be?

Acceleration of Free FallAcceleration of Free Fall

When air resistance doesn’t affect the When air resistance doesn’t affect the motion of a falling objectmotion of a falling object

Free falling objects gain speed at the rate of Free 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

GravityGravity

Objects in free fall gain speed because of Objects in free fall gain speed because of gravitygravity

Gravity is 9.8 m/sGravity is 9.8 m/s22

What is the motion of an object if you throw What is the motion of an object if you throw it up?it up?

Mass and InertiaMass and Inertia

The more massive the The more massive the more Inertiamore Inertia

The more FORCE The more FORCE needed needed

OROR

The less accelerationThe less acceleration

RememberRemember

Mass is not WeightMass is not Weight

Mass is not volumeMass is not volume

Mass is the amount of Mass is the amount of matter in an objectmatter in an object

Weight is ForceWeight is Force

Force due to gravity that act’s on an object’s Force 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

NewtonNewton

Standard unit of Standard unit of Weight/ForceWeight/Force

Symbol – NSymbol – N

F = maF = ma

One kilogram Weighs One kilogram Weighs 9.8 Newtons9.8 Newtons