Unit 2 Lesson 3: Speed, Velocity, & Acceleration

​Science Root of the Day:

DO NOW: Write what you think the example words mean in your lab manual.

Extra Credit: Find three additional words that use this root and write them and their definition in your lab manual (6 Points Max)

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Speed, Velocity, & Acceleration

Multiple Choice

What is the unit for force?

• Pound

• Newton

• Gram

• Liter

Multiple Choice

When we pour sand on an icy road, what force are we increasing to help cars stay on the road?

• electricity

• magnetism

• friction

• gravity

Multiple Choice

Friction is a force that acts in a/an ___________ direction of movement.

• similar

• opposite

• parallel

• upward

Multiple Choice

What is the net force?

• 20 N 

• 0 N 

• 400 N 

• 40 N 

Multiple Choice

Which direction will the box move? 

• To the left

• To the right

• Upwards

• Downwards

Lesson Objectives

• Distinguish between kinds of speed and Velocity

• Define Acceleration and distinguish it from Velocity And Speed

• Observe the acceleration of falling objects

Open Ended

Discuss with your neighbor: WITHOUT using the words "movement" or "motion" in your answer: What is "motion"?

Describing Motion

• 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

Defining Motion

• 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 to describe 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

Fill in the Blank

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

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

Match

Match the following values to the variable they correspond with

• ?

• 4.5

• 60

Distance

Time

Avg. Speed

• Distance

• Time

• Avg. Speed

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

Fill in the Blank

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

Fill in the Blank

What is the average speed of a cheetah that sprints 100m in 4 seconds?

Fill in the Blank

A runner races in the 100-meter dash.  It takes her 10 seconds to finish.  What is her average speed in m/s?

Fill in the Blank

Find speed when distance is 142 km and time is 2 hours in km/hour.

Velocity

• Velocity: A measurement of both speed and direction

  • A vector Quantity

  • How Fast and Where

• Velocity is calculated the same way 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

Fill in the Blank

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

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

Fill in the Blank

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

-

Fill in the Blank

An amusement park ride falls straight down for 4 seconds. During this time, the ride accelerates from 0 m/s to 40 m/s. What is the ride's rate of acceleration during this time?

Free Fall

• When an object is dropped from a height, it will accelerate during its fall

  • Gravity is a force that pulls on all objects

• Free Fall: When the only force acting on an object is gravity

  • On Earth, all objects accelerate at the same rate in free fall: 10 m/s²

• If you throw an object up in the air, it will stop for a split second and be at rest before dropping

Multiple Select

You are driving in a car. Select all of the actions that are considered to be acceleration.

• Turning right

• Speeding up

• Using the brakes

• Turning left

• Going in Reverse

Multiple Select

Which of the following measurements are vectors?

• speed

• velocity

• acceleration

• None of these are vectors