Distance:Distance: describes how far an object has describes how far an object has moved, regardless of its directionmoved, regardless of its directionex: 40km east + 25km west = 65 ex: 40km east + 25km west = 65 totaltotal km traveled km traveled

Displacement:Displacement: describes both distance describes both distance andand direction directionex: 40 km east + 25 km west = 15 km east ex: 40 km east + 25 km west = 15 km east

ex: 40 km east + 25 km east = 65 km east ex: 40 km east + 25 km east = 65 km east

How fast an object is traveling How fast an object is traveling regardless of directionregardless of direction

Unit: Unit: m m or or km km secsec hour hour

Described in two ways:Described in two ways:1. 1. Instantaneous speed:Instantaneous speed: measured at a specific instant measured at a specific instant

initial speed and final speed are examplesinitial speed and final speed are examples this is what speedometers measurethis is what speedometers measure

2. 2. Average speed:Average speed: total distance traveled per unit of time total distance traveled per unit of time if an object travels at a constant speed, then the if an object travels at a constant speed, then the

instantaneous and average speed will be equalinstantaneous and average speed will be equal if the object is traveling at varying speeds, then the average if the object is traveling at varying speeds, then the average

speed is calculated as total distance traveled over total timespeed is calculated as total distance traveled over total time

Describes both the speed of an object Describes both the speed of an object ANDAND its its direction of motiondirection of motion

Units: speed + direction: 24 Units: speed + direction: 24 m m north north sec sec

Measured in two ways:Measured in two ways:1. I1. Instantaneous velocity:nstantaneous velocity: velocity at a specific instant velocity at a specific instant2. 2. Average velocity:Average velocity: the total displacement per unit of the total displacement per unit of

timetime

Velocity can change if:Velocity can change if:1. the object’s speed is changed (increased or decreased)1. the object’s speed is changed (increased or decreased)2. the object’s direction can change2. the object’s direction can change

V = either velocity or speedV = either velocity or speed

d = distance or displacementd = distance or displacement

t = timet = time

Units count!!!!!!!!!!Units count!!!!!!!!!!Let’s practice!!!!Let’s practice!!!!

v = d t

1. What is the difference between distance and displacement?

2. What is the difference between speed and velocity?

3. Your average walking speed is 0.90 m/sec. What is it in km/hour?

FLASHBACK

1. EOC WORKBOOK - pg. 48 [1,2,4,5]2. Why do you think some people confuse

speed with velocity?

3. Does a speedometer show both speed and velocity?

4. You travel to and from RHHS, which is located 5 mi to the west of your house. What is your distance & displacement?

FLASHBACK

PS 5.3 and PS 5.4PS 5.3 and PS 5.4

The rate of change of an object’s The rate of change of an object’s velocity velocity over the time it takes for that change to over the time it takes for that change to occuroccur

Equation:Equation: a = a = (v(vff – v – vii)) t t

Unit: m/s/s or m/sUnit: m/s/s or m/s22 (most common) (most common)

However, the unit used for velocity (m/s) and However, the unit used for velocity (m/s) and the unit used for time (s) do not necessarily the unit used for time (s) do not necessarily need to be the same:need to be the same:

km/hr per secondkm/hr per second

The change in acceleration may involve a The change in acceleration may involve a change in speed or directionchange in speed or direction

Can acceleration be negative???Can acceleration be negative???

Yes!!Yes!!When you are slowing down at a When you are slowing down at a

stoplight, speed is decreasing, stoplight, speed is decreasing, so acceleration is opposite of so acceleration is opposite of

velocity... = negative velocity... = negative accelerationacceleration

1. constant acceleration1. constant acceleration: acceleration is zero: acceleration is zero because the velocity does not changebecause the velocity does not change

ex: walking 2 meters every 15 secondsex: walking 2 meters every 15 seconds

2. positive acceleration:2. positive acceleration: the object is the object isspeeding upspeeding up

ex: getting on the interstate in your carex: getting on the interstate in your car

3. negative acceleration3. negative acceleration:: the object isthe object isslowing downslowing down

ex: pulling into a parking lot to ex: pulling into a parking lot to park your carpark your car

A.A. All objects accelerate as they fall because All objects accelerate as they fall because the Earth exerts gravitational force on themthe Earth exerts gravitational force on them

B.B. All objects when released accelerate in the All objects when released accelerate in the direction of the force (downward)direction of the force (downward)

C.C. At initial release, the object has an initial At initial release, the object has an initial velocity of 0.0 m/secvelocity of 0.0 m/sec

D.D. As it falls, the object accelerates at a As it falls, the object accelerates at a constant rate of 9.8 m/sconstant rate of 9.8 m/s22

E.E. This means the object will travel 9.8 m/sec This means the object will travel 9.8 m/sec every second it is falling every second it is falling as long as there as long as there is no air resistanceis no air resistance

F.F. The value 9.8 m/secThe value 9.8 m/sec22 is called the is called the acceleration of gravityacceleration of gravity (a (agg).).

a = a = (v(vff – v – vii))

tt Positive Acceleration: (speeding up)

A jet airliner starts at rest and reached a speed of 80 m/s in 20 seconds. What is it’s acceleration?

a = a = (v(vff – v – vii))

tt Negative Acceleration: (slowing down)

A skateboarder is moving at a constant speed of 3 m/s and comes to a stop in 2 seconds. What is his acceleration?

Assignments!Assignments!

Right Now:

pg 51 “Self Check” # 1-4

Marble Lab!!!Marble Lab!!!

1. What needs to occur for an object to have acceleration?

2. Which of the following is a proper unit of acceleration?

a. m/km2 b. km/h c. m/s2 d. m2/s3. When describing the rate of a race car going

around a track, should you use the term speed or velocity, why?

4. How long does it take for the sound of thunder to travel 1485 m, if sound travels at 330 m/s?

FLASHBACK

1. If you ride your bike down a straight road for 500 m then ride back, your distance is ____ your displacement.

a. greater than b. less than c. equal to

2. Acceleration is rate of change of ____.a. position b. time c. velocity d. force

 3. If you ride your bike up a hill, then ride down

the other side, your acceleration is ____. a. all positive b. first positive, then

negative c. all negative d. first negative, then positive

FLASHBACK

Tennis Ball ActivityTennis Ball ActivityWhat changes when a tennis ball What changes when a tennis ball

bounces???bounces??? Draw and label for two bounces: Draw and label for two bounces:

1.1. Positive accelerationPositive acceleration

2.2. Negative accelerationNegative acceleration

3.3. Increasing and Increasing and

decreasing speeddecreasing speed

1. How long will it take to reach Bi-Lo 15 km away if traveling at 50 km/hr?

2. How long will it take a whale to travel 200 km swimming 4 m/s?

3. What is the value of 9.8 m/sec2 called…

4. What is the formula for acceleration?

FLASHBACK

PS 5.7PS 5.7

““The velocity of an object will remain constant The velocity of an object will remain constant unless a net force acts on it.” unless a net force acts on it.”

This is called the Law of Inertia. This is called the Law of Inertia.

Inertia:Inertia: is the tendency of an object to remain is the tendency of an object to remain at rest or in motionat rest or in motion

Inertia is dependent upon an object’s mass.Inertia is dependent upon an object’s mass.

Force:Force: a push or pull that one object exerts on a push or pull that one object exerts on anotheranother

It is measured in Newtons (N).It is measured in Newtons (N).

If one object has a greater force, then If one object has a greater force, then net force net force must must be calculatedbe calculated

How does this relate to Newton’s First Law?????

““When a net force acts on an object, it will When a net force acts on an object, it will accelerate in the direction of the net force”accelerate in the direction of the net force”

The larger the force, the greater the The larger the force, the greater the accelerationacceleration

The larger the mass, the smaller the rate of The larger the mass, the smaller the rate of accelerationacceleration

Force = Mass (acceleration)Force = Mass (acceleration)

Friction and air resistance can affect net Friction and air resistance can affect net force; they act as opposing forces.force; they act as opposing forces.

III. Newton’s Third LawIII. Newton’s Third Law

A.A. Newton’s Third Law :Newton’s Third Law : When one object When one object exerts a force on a second object, the exerts a force on a second object, the second object exerts a force on the first that second object exerts a force on the first that is equal in magnitude and opposite in is equal in magnitude and opposite in direction. direction.

1. a swimmer pushes on the water, and the 1. a swimmer pushes on the water, and the water pushes backwater pushes back

2. a ball thrown on a wall, bounces off2. a ball thrown on a wall, bounces off

Force, Mass, Weight, and Force, Mass, Weight, and GravityGravity

PS 5.8 – 5.10PS 5.8 – 5.10

I. The Math Behind the ForceI. The Math Behind the Force

A.A. Force is a derived unit; it involves multiplying Force is a derived unit; it involves multiplying the mass of an object by its acceleration:the mass of an object by its acceleration:F = mass * accelerationF = mass * acceleration

B. For us, the mass is measured in Kilograms (Kg) B. For us, the mass is measured in Kilograms (Kg) and the acceleration in m/secand the acceleration in m/sec22..

C. This means the final answer (Force) is C. This means the final answer (Force) is measured as Kg * m/secmeasured as Kg * m/sec2 2 or 1 Newtonor 1 Newton

D. 1 Newton is the amount of force required to D. 1 Newton is the amount of force required to accelerate a 1 Kg object at a rate of 1 m/secaccelerate a 1 Kg object at a rate of 1 m/sec22

E. Look at these examples:E. Look at these examples:

What is the force required to move a 2400Kg What is the force required to move a 2400Kg car with an acceleration of 4 m/seccar with an acceleration of 4 m/sec22??

If a force of 4.2 Newtons is applied to an If a force of 4.2 Newtons is applied to an object with a mass of 75 Kg, what is the rate object with a mass of 75 Kg, what is the rate of acceleration?of acceleration?

II. Newton’s Law of GravitationII. Newton’s Law of Gravitation

A.A. States that there is a force of attraction States that there is a force of attraction between all objects in the universe.between all objects in the universe.

B.B. The object with the larger mass will exert The object with the larger mass will exert the greater force. This is why objects weigh the greater force. This is why objects weigh more on the earth than on the moon. The more on the earth than on the moon. The earth is larger so it has a greater force of earth is larger so it has a greater force of attraction (gravity).attraction (gravity).

C.C. We do not notice the forces between most We do not notice the forces between most objects on earth because the force of the objects on earth because the force of the earth is so much greater than the force earth is so much greater than the force between the two objects.between the two objects.

D. The amount of force the earth exerts on D. The amount of force the earth exerts on an object is dependent upon the object’s an object is dependent upon the object’s mass & distance. The greater the mass, mass & distance. The greater the mass, the greater the gravitational force.the greater the gravitational force.

E. Weight is a measure of an object’s E. Weight is a measure of an object’s gravitational force and it can be found gravitational force and it can be found using the formula:using the formula:

FFww = mass (acceleration of gravity) = mass (acceleration of gravity)

F. The acceleration of gravity is what?F. The acceleration of gravity is what?

9.8 m/sec9.8 m/sec22

G. Try these examples:G. Try these examples:

What is the weight of an object with a What is the weight of an object with a mass of 10 Kg?mass of 10 Kg?

What is the mass of an object with a What is the mass of an object with a weight of 25 N?weight of 25 N?