Transcript Weight
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