Calculating Speed

Daily Science

• Write down the following words in your note section:

• Motion, reference point, acceleration, velocity

• With your groups discuss what each word means to you. Come up with a general idea and everybody needs to write it down

• Then answer the following question:

• How do you know an object is in motion?

Motion

• For an object to be in motion you must use a reference point

• A reference point is a stationary place or object used for comparison to determine if something is in motion.

• An object is in motion if it changes position relative to a reference point.

Calculating Speed

Two things are needed to calculate speed:

1. Distance the object travels.Units that are included: (meter (m), centimeter (cm),

kilometer (km), feet (ft.))

2. The time it takes the object to travel that distance.Units that are included: (seconds (s), minutes (min.),

hours (h))

Calculating Speed

When you know the distance and time of the object you need to use the following equation.

Speed = Distance/ Time or S=d/t

For example:An object that travels a distance of 10 meters in 2 seconds you would do this:

Calculating Speed

Since you know the distance and time you just put the numbers in the correct variables:d= 10 meterst= 2 seconds

Therefore you can find the speed:

s= 10m/2 sec.s= 5m/s

Always include the unit for distance and time in your answer (m/s).

Calculating Speed

To find the average speed of an object is similar to finding the average of a group of things:

All you need to do is add up all of the distances together and all the total time together and use the same equation.

For example:

A biker travels 32 km in 2 hours during the first leg of the race and on the second leg of the race he traveled 13 km in 1 hours.

Calculating Speed

Since we know the distance and time we can find the average speed of the biker:

The two distances that he traveled was 32 km and 13 kmThe two times he traveled that in was 1 hour and 2 hours

Add the distances together:

d= 32 km + 13 km = 45 kmt= 2 hour + 1 hour = 3 hours

s= 45 km/3 hourss= 15 km/hr

Calculating Speed

Speed doesn't tell us everything about the motion of an object.

To fully understand motion you also need to know the velocity of an object.

When you know the speed and direction of an object you know the velocity

Other Equations to Know

Speed= distance/time

Distance= Speed x Time

Time= Distance/Speed

Practice Problems

1. A car traveled 15 hours to travel a distance of 653 km. How fast was this car driving?

2. A person walked for 35 seconds with a speed of 1.5 m/s . How far did they walk?

3. A truck drove for 320 km at a speed of 35 km/h. How long did it take them?