5. • Mass is a measure of how much matter or
particles an object has.
• Weight is a measure of how strongly
gravity pulls on that matter
• So if you were to travel to the moon,
where gravity is weaker, what would
change?
• Just remember that the weight of an object
depends on where it is, while its mass
stays the same.
6. • I have two bags, both the same shape and
size. One bag contains feathers and the
other contains bricks. Which is heavier?..
• Which is heavier a ton of bricks or a ton of
feathers?..
7. Gravity – what is it?
• is an attractive force between objects
with mass.
• Gravity acts on the Earth by ppuulllliinngg
objects towards its centre.
• An object with heavier mass has a
stronger gravitational pull = has a
heavier weight.
8. Gravity – what is it?
Which aarrrrooww iiss ppooiinnttiinngg
tthhee wwrroonngg wwaayy??
10. Who discovered it?
• It was Sir Isaac Newton
that ‘worked-out’ gravity.
• 1643 – 1727
• He was the greatest
English mathematician of
his generation. His work
on optics and gravitation
make him one of the
greatest scientists the
world has known.
11. Who discovered it?
The story goes that he was
sitting under an apple tree
and an apple fell onto his
head. He went to explore
why it fell down and came up
with a theory and
mathematical equation.. He
named it GRAVITY.
12. How do we measure it?
• We measure all forces in
Newton. The effect of gravity
gives us our weight - so our
weight should always be in
Newton.
• It is mass which is measured in
kilograms.
Newtonmeter (also called
Forcemeter, Spring balance,
and Pullmeter)
13.
14. Gravity on
Earth
causes this
man to
accelerate
downwards.
Its effect is
the same
everywhere.
17. The astronaut has a mass of 80kg
but when will he weigh more?
on the Moon on the Earth
Gravity = 1.5 Gravity = 10
Weight = 80 x1.5
Weight =
Weight = 80 x 10
120 N Weight = 800 N
18. NAME OF
OBJECT
MASS
(grams)
To
convert in
to KG we
(÷1000)
MASS
(Kilograms)
The pull
ofGravity
is 10 so
we (x10)
WEIGHT
(Newtons)
A packet of
crisps
125g
A car
1500kg
10 bags of
sugar
10,000g
A football
400g
A mobile
phone
250N
Teacher notes:
Talk about man on the moon – did he walk normally? (No) It was the gravity that made him so light. Why didn’t the space rocket ‘fly’ off too? (It’s mass was much greater than a man!) Going to the moon is one sure way to lose weight!
You might want to go further and talk about walking on Jupiter (has a much greater mass) and gravitational pull is stronger, so walking would be impossible. We would be much heavier on Jupiter! We might look very different if our planet’s mass was much greater – we would have had to evolve to cope with a much stronger gravitational pull.. maybe we’d be short and squat!
Teacher notes:
Talk about man on the moon – did he walk normally? (No) It was the gravity that made him so light. Why didn’t the space rocket ‘fly’ off too? (It’s mass was much greater than a man!) Going to the moon is one sure way to lose weight!
You might want to go further and talk about walking on Jupiter (has a much greater mass) and gravitational pull is stronger, so walking would be impossible. We would be much heavier on Jupiter! We might look very different if our planet’s mass was much greater – we would have had to evolve to cope with a much stronger gravitational pull.. maybe we’d be short and squat!
Teacher notes:
Talk about man on the moon – did he walk normally? (No) It was the gravity that made him so light. Why didn’t the space rocket ‘fly’ off too? (It’s mass was much greater than a man!) Going to the moon is one sure way to lose weight!
You might want to go further and talk about walking on Jupiter (has a much greater mass) and gravitational pull is stronger, so walking would be impossible. We would be much heavier on Jupiter! We might look very different if our planet’s mass was much greater – we would have had to evolve to cope with a much stronger gravitational pull.. maybe we’d be short and squat!
Teacher Notes
Although Newton and major scientists aren’t what we have to teach – it’s general knowledge. However, it’s also good to teach as another scientist (Einstein) did turn up in the 2006 SATs.
Obviously, gravity wasn’t ‘discovered’ but it was Newton that formulated ideas and named it so.
The apple story is not formally recorded and may be apocryphal, but it aids the memory nonetheless (and is fun).
Teacher Notes
Although Newton and major scientists aren’t what we have to teach – it’s general knowledge. However, it’s also good to teach as another scientist (Einstein) did turn up in the 2006 SATs.
Obviously, gravity wasn’t ‘discovered’ but it was Newton that formulated ideas and named it so.
The apple story is not formally recorded and may be apocryphal, but it aids the memory nonetheless (and is fun).
