Weight
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

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
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

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
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
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

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
Class Activity
Do calculation 1, 2, 3, 6,
 6 minutes


Calculations 4, 5 homework
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
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


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
Recap = Mass & Weight
Weight
Mass
 Measured in Newtons
 Measured in
(N)
kilograms (kg)
 Varies, depends on
 Is fixed, never
where you are
changes
 Is a force or a pull on
 Is a fixed property of something
all things, like length
or volume
Calculation 3
 An
object of mass 50 kg has a
weight of ___________ on earth
 1kg
= 10 N
 50 kg = 500N
 Answer 500N
Calculation 6

The mass of a man who weighs 550 N
on earth is ___________
1 kg = 10 N
 ? Kg = 550N
 Answer 55 kg

Where would I weigh more?
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!
 Homework
calculations 4 and 5

An astronaut has a mass of 124 kg

His weight on earth is 1240 kg/N, on the
moon is 207.08 kg/N and inouter space
is 0 kg/N. His mass , unlike his weight
never varies wherever he is
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