Unit 2 Lesson 3: Speed, Velocity, & Acceleration

• Distinguish between kinds of speed and Velocity

• Define Acceleration and distinguish it from Velocity And Speed

• Observe the acceleration of falling objects

• There are two aspects to motion

  • A change in position

  • ​The passage of time

• Motion is described Relative to something that isn't moving, or "at rest"

  • Example: If you are in a car with others, you are in motion relative to the ​outside of the car, but not in motion relative to the other people in the car

• Motion: the act or process of changing position relative to some reference during a period of time

  • There are three measurements used to describe any motion

    • Speed

    • Velocity

    • Acceleration​

Speed

• Before Galileo, motion was described as either "slow" or "fast"

• In His experiments, Galileo became the first to define and measure speed

• Speed: The amount of distance covered per amount of time

  • Any Combination of distance and time units can be used for speed

    • example: km/minute, miles/hour

Types of Speed

• There are different types of speed because there are different aspects of motion

  • Instantaneous Speed: The speed at any given moment of measurement

  • Average Speed: The speed over a given period of time

Average Speed Sample Problem 1

• You drive a total of 320 km in 4 hours. What was your average speed?

  • Step 1: Identify your variables

    • d= 320 km

    • t= 4 hr

    • Avg. Speed =?

  • Step 2: Plug in your variables to your average speed equation

Average Speed Sample Problem 2

• A car is traveling at an average speed of 60 km/hour. How far will it travel in 4.5 hours?

  • Step 1: Identify your variables

    • d=

    • t=

    • Avg Speed=

  • Step 2: Plug in your variables to your average speed equation

Calculating Average Speed Sample 2

• A car is traveling at an average speed of 60 km/hour. How far will it travel in 4.5 hours?

  • Step 1: Identify your variables

    • d= ?

    • t= 4.5

    • Avg Speed= 60

  • Step 2: Plug in your variables to your average speed equation

Velocity

• Velocity: A measurement of both speed and direction

  • A vector Quantity

  • How Fast and Where

• Velocity is calculated with the same equation as speed, but you include the direction in your final answer

  • Example: 60 Km/hour North

Acceleration

• Moving things tend to change their speed and velocity as they move

• Acceleration: Any Change in the velocity of an object

  • Can be going faster or slower

  • Can involve changing the Direction

• Is a vector

• Units: distance/s²

Calculating Acceleration Sample Problem 1

• Ted is driving to work. In 1 hour, Ted increases his velocity from 30km/h to 35 km/h. What is his acceleration?

  • Step 1: Identify Variables

    • V_f =

    • V_i =

    • t=

Acceleration Sample Problem 1

• Ted is driving to work. In 1hour, Ted increases his velocity from 30km/h to 35 km/h. What is his acceleration?

  • Step 1: Identify Variables

    • V_f =35

    • V_i =30

    • t=1

  • Step 2: Plug in Values and solve

Acceleration Sample Problem 2

• In 2.0 Seconds, a bike slows down from 8km/s to a complete stop. What is its acceleration?

  • Step 1: Identify Variables

    • V_f =

    • V_i =

    • t=

Acceleration Sample Problem 2

• In 2.0 Seconds, a bike slows down from 8km/sec to a complete stop. What is its acceleration?

  • Step 1: Identify Variables

    • V_f =0

    • V_i =8

    • t=2

  • Step 2: Plug Values into Equation and solve