8.6B Speed, Velocity, and AccelerationOn Level Notes

You will learn:

State Objective:Differentiate between speed, velocity, and acceleration

I can:If I give you real-life examples, can you tell me the difference between speed, velocity, and acceleration

Read graphs with data about speed and acceleration

Speed: the distance an object goes over a period of time

Different Types of Speed • Average Speed• Most common• Will have a distance figure and a time figure

• Constant Speed• Speed does not change• On a speed graph, this looks like a rising, diagonal line• On an acceleration graph, this looks like a flat plateau

Constant Speed in Graphs

The are both graphs for the same thing: constant speed

The graph on the left has distance over time (speed). The graph on the right is speed over time (acceleration).

Always read the axes to make sure you know what its showing you.

How to calculate average speed from a graph?

1. Write your formula: s= d/t2. Check your axes3. Plug in your values4. Calculate your answer

Practice Calculating Speed

1. What is on the Y axis? What is on the X axis?2. To calculate speed, what 2 values do you need?3. At one second, what was the average speed of this object in

m/s? Decimals are ok…just round to the nearest tenths place.4. Is the object moving between 19 and 20 seconds? How do you

know?

Velocity: speed with direction• Speed and velocity are almost the same• Velocity is different because it includes the direction the

object is traveling• If you are solving for velocity, you use the speed triangle• Your answer should include a directionDirection:North UpSouth DownEast LeftWest Right

Can you find the velocity?

30 m/s South 20 miles per hour

.6 mm / year to the right 348 seconds

½ mile 30 miles to the west

4 inches/yr left .97 m/s/s

85 km/min 29 cm/sec North

Velocity on a graphLook at the graph from earlier. Notice how this is distance over time, but they use the word “velocity”

Who uses velocity?• Airplane pilots• They need to know how fast AND which direction they need to go

• Meteorologists (Weather People)• They study the speed and direction of storms…just like the ice

storm we just had!

• Military Positions• They need to know at what angle to fire missiles, launch

satellites, direct unmanned drones.

Acceleration: 3 ways to accelerateFancy Definition: rate of how the velocity changes

What it really means: Acceleration is speeding up, slowing down, or changing direction.

Yes, it is really 3 things and not just speeding up.

Acceleration: caused by forces

Acceleration is caused by unbalanced forces.

To speed up, we need to apply a force to increase the speed of the object.

To slow down, we need to apply a force in the front of the object to decrease the speed.

Even if the object’s speed doesn’t change, a force is require to change its direction.

Acceleration on a GraphThe Y axis is velocity or speedThe X axis is time

Compare Speed and Acceleration on a GraphReally focus on your axes – which is it: speed or acceleration?

This shows an object speeding up over time.

Relationship: as the time increases, the acceleration increases

Comparing Speeds: moving or not moving

These 2 graphs show balanced forces: the one on the left is moving in a straight line in a constant speed. The one on the right is at rest and will not move unless a force moves it.

Distance over time variety

This graph shows the movement of an object over a period of time.

Comparing acceleration: changing speed or same speedNotice that this is speed over time: acceleration

Exit Ticket

1. What is the formula for Speed?

2. What is velocity?

3. What 3 ways can you accelerate?