Describing Motion

Chapter 2

1. Speed

• How fast you are going ?

1. Average Speed

• The distance traveled divided by the time of travel
• Average Speed = distance traveled/time of travel
• s = d/t
• 55 mph

1. Instantaneous Speed

• How fast you are going at a given instant
• Gives little indication how long it will take to cover a certain distance.
• The rate at which distance is being covered at a given instant in time.

1. Velocity

• Involves the direction of motion as well as how fast the object is going (velocity = speed and direction)
• Vector quantity
• Velocity = distance/time (v = d/t)
• 55 mph due east
• A force is required to change the velocity (friction)

1. Instantaneous Velocity

• The velocity of an object at a particular instant in time

1. Average Velocity

• The velocity of an object over a certain time period

C) Application: Racing Car Tires

1. Acceleration

• Vector quantity
• The rate at which velocity changes
• Acceleration = velocity/time (a = v/t)

1. Instantaneous acceleration

• The rate at which velocity is changing at a given instant in time.

1. Average acceleration

• The change in velocity divided by the time required to produce that change

v₁ = 0 m/s v₂ = 20 m/s

1. Direction of an acceleration

• Velocity is increasing

• Velocity is decreasing