Topic:Distance, Speed,

and VelocityUnit 1: Chapter 1

What is Distance and how do we measure it?• Definition:• Describes how far it is from one point to another

• Distance is measured in units of length• The SI unit for length is the meter (m)• Short distances are measured in centimeters (cm)• Long distances are measure in kilometers (km)

What is Speed and how do we measure it?• Definition:• How fast or slow something moves

• Speed determines how far something travels in a given amount of time

• The SI unit for speed is meters per second (m/s)• Other common units for speed

• Kilometers per hour (km/h)• Miles per hour (mph)• Centimeters per second (cm/sec)

What is Instantaneous Speed?

• Definition:• Speed at any given instant

• Difficult to calculate

• When you look down at the speedometer, you are observing instantaneous speed

What is Average Speed?

• Practice: • It took an airplane 3,600 seconds

to travel 540 km. What was the average speed of the airplane?

• What is the speed of a car that traveled 75 km in 1.5 hours?

• Even if speed varies during a trip, it is possible to calculate average speed

Calculating Distance or Time from Speed• If you know average speed you

can calculate:• Distance• Time

• To calculate distance:• Distance = speed x time

• To calculate time:• Time = distance/ speed

• Practice:• If a car travels at an average speed

of 60km/h for 5 hours, what distance did it travel?

• If you walk 6km at an average speed of 3 km/h, how much time does it take?

Speed Triangle

Speed vs. Velocity

• Speed tells us how fast or slow an object is moving but nothing about direction

• Definition:• Velocity is the measure of both speed and

direction

• Velocity represents two components of motion:• Speed• Direction

How do we represent velocity?

• Velocity is a vector

• Definition:• A vector is a measurement that

includes both size and direction

• Vectors are often represented by arrows

• The length of the arrow stands for speed

• The direction the arrow points indicates direction

How do you calculate velocity?

• You can calculate the average velocity of and object that is not changing direction

• Practice:• Toni’s dog is racing down the

sidewalk toward the east. The dog travels 35 meters in 18 seconds before it stops running. What is the velocity of the dog?