Today’s Objectives-Learn what vector and scalar quantities are

-Be able to distinguish between vector and scalar quantities

-Learn if some common measurements (speed, weight…) are vector or scalar quantities

-Learn the differences between speed and velocity

-Learn the difference between displacement and distance

What is a Scalar Quantity?

Scalar quantities have only magnitude (=how much)

Examples: • 10 meters• 2 liters• 20 kilometers per hour• 30 baht

What is a Scalar Quantity?

Scalar quantities have only magnitude (=how much)

Examples: • 10 meters• 2 liters• 20 kilometers per hour• 30 baht

Scalar10 meters

What is a Vector Quantity?

Vector quantities have magnitude AND direction

Examples: • 10 meters to the northeast (=displacement)• 100 kilometers and hour to the west (=velocity)

What is a Vector Quantity?

Vector quantities have magnitude AND direction

Examples: • 10 meters to the northeast (=displacement)• 100 kilometers and hour to the west (=velocity)

10 meters to the NEVector

Why are Vectors Important?

Can an asteroid’s path be described using vectors?

Yes! Asteroids have speed AND a direction

We know when meteor showers are coming because of our understanding of vectors

Practice

Label each quantity scalar or vector

1. 80GB2. 20 meters per second to the north3. 20 degrees Celsius4. 25 centimeters5. 8 Newton force upward6. 35 seconds7. 1.3 billion people in China8. 80 kilograms

AnswersLabel each quantity scalar or vector

1. 80GB no direction = scalar2. 20 meters per second to the north has a magnitude and

direction = vector 3. 20 degrees Celsius no direction = scalar4. 25 centimeters no direction = scalar5. 8 Newton force upward magnitude and direction = vector6. 35 seconds no direction = scalar 7. 1.3 billion people in China no direction = scalar8. 80 kilograms no direction = scalar

Displacement vs DistanceDistance – how far something moved (meters)

Displacement – how far, AND what direction something moved (meters to the NW)

18 m to the NW

18 kmSCALAR

Displacement Distance

VECTOR

Displacement vs DistanceDistance – how far something moved (meters)

Displacement – how far, AND what direction something moved (meters to the NW)

Is the red or yellow line distance?Red is distance = how far moved

DISPLACEMENT

DISTANCE

Yellow is displacement = how far and what direction

Displacement is always a straight line, and will always be shorter than distance

Start

Finish

Displacement vs DistanceDistance – how far something moved (meters)

Displacement – how far, AND what direction something moved (meters to the NW)

Classwork:1. A man walks around the outside of park and ends up in the same spot he started.

What is his displacement? How much distance did he travel?

1km

PARK1km 1km

1km

Finish

Start

*His displacement is 0 *His distance traveled is 4 km

*Scalar or vector?

SpeedSpeed is how fast an object is traveling

Speed = distance (in meters)

s = d

It takes a swimmer 57.2 seconds to swim a distance of 100 m. What is the swimmer’s average speed?

time (in seconds)

t

SpeedSpeed is how fast an object is traveling

Speed = distance (in meters)

s = d

It takes a swimmer 57.2 seconds to swim a distance of 100 m. What is the swimmer’s average speed?

= 100m = 1.75 m/s

time (in seconds)

t

s = dt 57.2s

SpeedSpeed is how fast an object is traveling

Speed = distance (in meters)

s = d

It takes a swimmer 57.2 seconds to swim a distance of 100 m. What is the swimmer’s average speed?

= 100m = 1.75 m/s

time (in seconds)

t

s = dt 57.2s Scalar or vector??

SpeedSpeed is how fast an object is traveling

Speed = distance (in meters)

s = d

It takes a swimmer 57.2 seconds to swim a distance of 100 m. What is the swimmer’s average speed?

= 100m = 1.75 m/s

time (in seconds)

t

s = dt 57.2s Scalar or vector?? Scalar

No direction

VelocityVelocity is how fast an object is going, AND its direction

Velocity = displacement (in meters) time (in seconds)Remember, displacement is distance AND direction

If you need to go from point A to point B in 10 minutes, what velocity do you need to get there on time?

Velocity = 3.7 km east = 0.37 km east/ minute 10 minutes

3.7 kmA B N

S

W E

Scalar or vector? Vector because has direction

Speed vs VelocitySpeed – how fast something is moving (m/s)

Velocity – direction and speed of an object (displacement/s)

Speed vs VelocitySpeed – how fast something is moving (m/s)

Velocity – direction and speed of an object (displacement/s)

If I say “I’m driving 85 kilometers per hour in Chiang Mai”, is that a vector or scalar measurement??

Speed vs VelocitySpeed – how fast something is moving (m/s)

Velocity – direction and speed of an object (displacement/s)

If I say “I’m driving 85 kilometers per hour in Chiang Mai”, is that a vector or scalar measurement?? Speed has no direction = Scalar

Speed vs VelocitySpeed – how fast something is moving (m/s)

Velocity – direction and speed of an object (displacement/s)

If I say “I’m driving 85 kilometers per hour in Chiang Mai”, is that a vector or scalar measurement?? Speed has no direction = Scalar

If I say “I’m driving 85 kilometers and hour north toward Chiang Mai”, is that a vector or scalar measurement??

Speed vs VelocitySpeed – how fast something is moving (m/s)

Velocity – direction and speed of an object (displacement/s)

If I say “I’m driving 85 kilometers per hour in Chiang Mai”, is that a vector or scalar measurement?? Speed has no direction = Scalar

If I say “I’m driving 85 kilometers and hour north toward Chiang Mai”, is that a vector or scalar measurement?? Velocity has speed and direction = Vector

Speed 20 meters/second Length 12m Displacement 10m to the north Volume 3 Liters Area 23 meters squared Mass 29 grams Velocity 60km/h to the north Force 56 Newtons down

Measurement Example Vector or Scalar

no direction = scalar no direction = scalar

direction = vectorno direction = scalarno direction = scalarno direction = scalar

direction = vectordirection = vector

Some Common Measurements

Decide Scalar or VectorScalar Vector

LengthAreaVolumeSpeedDisplacementVelocityMassForce

Energy

TimeTemperature

Remember…Scalar quantity has no directionVector quantity has directionDisplacement is distance with directionVelocity is speed with direction

Don’t let these words scare you, they sound complicated, but they really aren’t.

Complete Questions in NotebookDirections: Write vector or scalar1. 40 baht ______________2. 20 Joules ______________3. 1.2 billion atoms ______________4. 28 degrees Celsius ______________5. 8 km/hr west ______________6. 25 N down ______________7. 3 Liters ______________8. 23 km/hr in Bangkok______________9. 10 m west ______________10. 79 kg ______________

Directions: fill in11. Velocity is speed with __________.12. Displacement is direction and __________. A mountain bike rider followed the red line13. What was his displacement?14. What was his distance traveled?

53km

Start

Finish

27km NE

Measurement Scalar or Vector

15. Mass

16. Displacement

17. Area

18. Velocity

19. Force

20. Speed

21. Weight

15-21 Complete the table

Write questions and answers in notebook