Calculating Speed

...calculating speed...

Objectives:

Usain Bolt.

Mad running skills.

• Be able to solve numerical problems by calculating speeds, distances, and times.

• Be able to rearrange an equation using an equation triangle.

• Be able to present a calculation correctly, and choose the right units to go with your answer.

Task 1 - Starter

Scream if you want to go faster, okay?

Find someone who:

1) knows 5 different units we can use to measure speed.

2) can describe an experiment we could carry out to find the speed of a person running.

Task 2 - Which units should we use?

Go Turbo!

Complete the sentences by choosing an appropriate unit of speed for each of the things in the list.

The first one has been done for you!

Click the image above to download this task as a word document.

Task 3 - Using an equation triangle

Calculations! Yeah!

We can use a simple formula to solve numerical problems involving speeds, distances and times.

D = S × t

D = Distance, measured in metres (m)

S = speed, measured in metres per second (m/s)

t = time, measured in seconds (s)

Your teacher will show you how to use an equation triangle to rearrange the formula.

Working in pairs, write all the different versions of the formula on the mini-whiteboards to check you understand!

Task 4 - Calculations

Your teacher will show you how to use the formula to solve a numerical problem, and how to present a calculation correctly.

Example calculations:

1. A student runs 80m in 20 seconds. Calculate the student's speed.

2. A car is travelling at 30m/s. How far will it travel in 60 seconds?

3. A cyclist is moving at 11m/s. How long will it take her to travel 1km?

Some for you to try

Go Turbo!

Solve the problems on this worksheet.

Click the image above to download this task as a word document.

This alternative version of the worksheet has space for examples.

...or higher tier groups could try these questions.

Click the image above to download this task as a word document.

Some of these problems involve a change of units.

This alternative version of the worksheet has space for examples.

Extension: A car takes 5 minutes to cover 2km. What is the car's speed in km/min? What is the car's speed in m/s? How long will it take to travel 12.5km?

Task 5 - Plenary - adding speeds

Think hard!

As fast as a speeding train!

Speeds can appear different when measured from different viewpoints. For each of the scenarios below, think about:

What speed would you measure from inside the moving vehicle?

What speed would you measure from outside the moving vehicle?

What path would the object appear to follow from each perspective?

1) Running forwards at 4m/s on a train travelling at 40m/s.

2) Walking backwards at 2m/s on a train travelling at 40m/s.

3) Throwing a ball sideways at 10m/s from a car travelling at 30m/s.

4) Throwing a ball upwards at 10m/s on a train travelling at 20m/s.

5) Throwing a ball at 15m/s towards a train travelling at 50m/s.

(Think about what speed you would see the ball move away from you, and what speed the train driver would see the ball come towards him!)

Extension: If the bouncy ball in question 5 had a coefficient of restitution of 0.8, what speed the ball will bounce off of the train, from each persons perspective?

Homework

Homework :)

Woop woop!

Your teacher will give you some calculations to try at home.

Remember to show full working for all calculations, and to give units with your answers!

No digital worksheet available for this at the moment. If you would like to contribute one, it will be gratefully appreciated!