Motion and Speed: Page 66

QUESTION: Are we moving right now?

OBJECTIVE: Students will be able to calculate speed when given the distance and the time.

VOCABULARY: motion speed velocity

Motion and SpeedWrite these questions onto page 66

SKIP ONE LINE BETWEEN EACH QUESTION

1. How can you tell if an object is in motion?2. What are the equations for calculating speed, distance and

time?

Am I in motion?It’s usually pretty easy to tell if you’re in motion.

We look at objects that we know don’t move, like a building or a tree, these objects are called reference points. Then we see if our position is changing compared to the reference point.

Sometimes, it’s not so easy to tell if you’re moving.

Sometimes, it’s hard to find a reference point. Like when you’re flying.

Has this ever happened to you?Have you ever been on a stopped train with another stopped train on the next track?

Suddenly, one of the trains starts to move, but you can’t tell which one. Why can’t you tell what’s moving?

The other train is blocking out any reference points. All you can see is the other train and you don’t know if it’s stopped or moving. You have no reference points.

Calculating SpeedSpeed is the distance an object travels divided by the time it takes to travel that distance.

Speed = Distance Time

If a person walks 8 meters is 2 hours, then:

Speed = 8 meters 2 hours

Speed = 4 meters hour

What’s Average Speed?When you are driven to the mall, do you go the exact same speed for the whole trip?

Average Speed = Total Distance Total Time

To find how fast you went for the entire trip you calculate your average speed.

No. You have to back out of the driveway. There are red lights where you have to stop, and there are places where you can drive fast.

Average Speed = 25 miles = 50 miles .5 hrs hour

So a trip to the mall a distance of 25 miles away that took 30 minutes (.5 hours) would be calculated like this

Calculating Time and DistanceIf you know the speed and distance you can calculate the time using the equation below.

Time = Distance Speed

If you know the speed and time you can calculate the distance using the equation below.

Distance = time * speed

What’s Velocity?If two cars are in an accident and one car is traveling 80 miles per hour and the other car is traveling 79 miles per hour, do you think it was a serious accident?

Maybe not. What if the cars were traveling in the same direction? Would the two cars hit each other that hard?

If the cars were traveling in opposite directions, that would be a real problem.

To know how bad the cars hit you need to know both the speed and the direction. This is called, velocity.

Calculating Speed: page 66Check that the answers to these

questions are in your notes.

1. How can you tell if an object is in motion?2. What are the equations for calculating speed, distance and

time?

VOCABULARY

Motion- the change in the position of an object.

Speed-the distance an object travels divided by the time it takes to go that distance.

Velocity-the speed and direction of an object’s motion