1. Weight

2. Weight The earth exerts a force on everything
This force is called gravity
What does gravity do?
Hold your pen up and then let go
Why does this happen

3. Weight The force the earth exerts on me is called my weigh
The weight of a body is the force pulling it towards the center of the earth
Like all forces, weight is measured in newtons

4. Weight So what is your weight, how do you measure your weight
We are all made of matter, some people have a grater matter than others
The more matter an object has the greater will be the force acting on it

5. A block of lead would have a greater mass than a block of wood of equal size
Force of gravity acting on the block of lead would be greater than the force of gravity acting on the block of wood.
The block of lead has a greater weight
So the weight of a object is determined by two things the mass of it, and the fore of gravity acting on it

6. Weight Does your weight change when your in the moon or space
Your weight changed because the pull of gravity on it changes
What is weight again = The force the earth exerts on an object
Will a litre of milk weigh the same on the earth, moon and space

11. Weight
The litre of milk will be 6 times lighter on the moon compared to earth
The moon is one-sixth the size of the earth
The force of gravity acting on an object is one-sixth, of the force acting on earth
The moon has a force of 1.67 on 1kg

12. The litre of milk will be weightless in space
Your weight is zero in space, that’s why you can float because there is no force of gravity acting on you
Things also wheigh less on the top of a mountain
Instead of a force of 10 N it would be 9 N

13. Class Activity Do calculation 1, 2, 3, 6, 6 minutes
Calculations 4, 5 homework

14. Calculations 1 A litre of milk (1kg) on the earth weighs
1kg x 10N = 10 N/kg
A litre of milk on the moon weighs
1 kg x 1.67N = 1.67 N/Kg
A litre of milk in space weights
1 kg x 0 = 0 N/kg
A litre of milk on the top of a mountain weighs
1 kg x 9N = 9 N/Kg

15. Calculation 2 What is the object weighed 600kg, what would it weigh
Earth= 600 kg x 10N = 6000 kg/N
Moon= 600 kg x 1.67N = 1002 kg/N
Space= 600 kg x 0N = 0 kg/N
Mountain= 600 kg x 9N = 5400 kg/N

16. Is it still milk inside
Is it still a litre
So this states that mass stays the same
If you are standing on the earth , moon and space you have the same mass but your weight changes

17. Recap = Mass & Weight Weight Measured in Newtons (N) Mass
Varies, depends on where you are
Is a force or a pull on something
Mass
Measured in kilograms (kg)
Is fixed, never changes
Is a fixed property of all things, like length or volume

18. Calculation 3
An object of mass 50 kg has a weight of ___________ on earth
1kg = 10 N
50 kg = 500N
Answer 500N

19. Calculation 6
The mass of a man who weighs 550 N on earth is ___________
1 kg = 10 N
? Kg = 550N
Answer 55 kg

20. Where would I weigh more?
The first picture is just someone on a boat – this may cause a surprise, but the point is to emphasise that at sea level you would weigh more than on high ground, and you would weigh even more when deep sea diving.

21. Long Jump Record
Why did Bob Beaman’s 1972 long jump record (8.9 metres) last until 1991?
The Olympics were held in Mexico city….he weighed less!

23. Homework calculations 4 and 5

24. An astronaut has a mass of 124 kg
His weight on earth is 1240 kg/N, on the moon is kg/N and inouter space is 0 kg/N. His mass , unlike his weight never varies wherever he is

25. Calculating Weight 5 Find the weight of a 250g bag of biscuits
Solution:
First change the mass to kg
250g = 0.25 kg (250g ÷ 1000)
Now, F = 0.25kg * 10 m/s2
= 2.5 kg/m2
= 2.5 N
Stress the importance of having units in kg before you begin calculation