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Rogue Physicist.  Free resources for physics education © 2006-2016 Dorian Pascoe.  Email: dorian@top-school.co.uk

Most resources are available under a Creative Commons Licence.  Visit our mirror at www.physicsweb.altervista.org

 

 

 

...mass and weight...

 

 

 

Objectives:

 

  
 

 

Think hard!

Mass and weight...

  

 

• Understand the difference between mass and weight.

 

 

• Be able to convert between mass and weight using 1kg = 10N on Earth.

 

 

• Be able to use the formula W = m × g to solve numerical problems involving mass and weight.

 

  

 

 

 

 

 

 

 

Task 1 - Starter:

 

  
 

 

I know the answer!

  

 

Find someone who knows:

 

 

1) The difference between reaction time and thinking distance.

 

2) The difference between stopping distance and braking distance.

 

3) The factors which affect only thinking distance.

 

4) The factors which affect only braking distance.

 

5) The factor which affects both thinking distance and braking distance.

 

 

 

Your teacher will tell you which questions to answer.

 

  

 

 

 

 

 

 

 

Task 2 - Mass or weight?

 

  
 

 

Weight - I need t

  

 

The term weight is commonly misused in everyday language.  When most people say weight they usually mean mass.  You need to know what both terms mean, and be able to use them correctly.

 

 

Look at this powerpoint presentation which explains the difference between the two terms.

Click the image above to open the presentation.  Note that this is secure content and is only accessible using a password, due to licensing restrictions.

 

  

 

 

 

 

 

 

 

Task 3 - An annoying song

 

  
 

 

 

I want to sing along!

 

 

 

 

 

  

 

This really annoying song will get stuck in your head and help you to remember the difference between mass and weight, as well as the correct units for each!

 

 

Video credit: YouTube

 

 

  

 

 

 

 

 

 

 

Task 4a - Formula

 

  
 

 

Calculations! Yeah!

 

  

 

Mass and weight are connected by a simple formula:

 

 

W = m × g

 

 

Where:

 

W = weight, measured in Newtons (N)

m = mass measured in kilograms (kg)

g = gravitational field strength (9.8 N/kg on earth)

 

 

This can also be written in an equation triangle:

 

 

 

Note: the formula is given in the examination, but the equation triangle is not given.  If you find it easier to use the equation triangle then it is up to you to remember it!  You must also remember the units for each quantity.

 

  

 

 

 

 

 

 

Task 4b - Calculations

 

  
 

 

Calculations!

AWESOME!

 

  

 

Use the equation to calculate the weight of each of these masses.  Remember, you will need to convert the units where necessary!

 

 

 

When you have finished, try these problems, which are a little more difficult and require you to manipulate the formula, as well as calculating weights on different planets!  Show full working for each calculation.

 

  

 

 

 

 

 

 

Task 5

 

  
 

 

Think hard!

Read this comic on Earth, or a suitable alternative planet.

  

 

Read this comic strip.  Think about how variations in gravitational field strength might affect our ideas about sporting achievements and record.

 

Image credit: XKCD.