# Forces and gravity topic PowerPoint presentation

```FORCES
Is gravity real or does the Earth
just suck?
What do forces do?
Make things ---move

move faster

move slower

change direction
also
change shape
2
Big and Little
forces
We can measure forces
Using a forcemeter
3
Sir Isaac
Newton
4
Which fruit ?
5
Newton?
6
Gravity is a force
 When
gravity pulls something
towards the Earth - we call this force the weight.
7
Forces are measured in
Newtons
Weight of an apple = about 1 Newton
8
Let’s play
a game !
9
Results
Measurement
in Newtons
A
B
C
Predicted
Real
10
Forcemeters
11

Now another game!
12
Lifting a ping pong ball
.
Suck !
straw
13
ping pong ball falling
The arrow represents the
force of gravity
14
The ball does not fall when your
sucking force = force of gravity
Suck
straw
How
have I
shown
this ?
gravity
15
Which diagram shows the sucking
force equal to the force of gravity?
Suck
Suck
Suck
straw
straw
straw
gravity
gravity
gravity16
The ball does not fall when your
upward force = force of gravity
Suck
straw
gravity
17
Gravity down under

People
do not
fall off
the
Earth
18
two
objects
dropped
at the
same time
19
On the Moon – Apollo 15
A heavy geological hammer
and a falcon feather were
dropped from the same
height.
They hit the lunar surface at
the same time.
astronaut David Scott

NASA pictures
http://nssdc.gsfc.nasa.gov/planetary/image/featherdrop_sound.mov
20
Hippo jump
21
Hippo jump
Force of gravity
22
Saved?
23
Hippo is still
falling quickly
24
Hippo is still falling
quickly
air resistance
but not getting
faster

How do we know?
Force of gravity
25
How can we slow Hippo
down?

What can you change?
26
Launching a satellite
The cannon
ball must
move
very
quickly to
orbit the
earth.
The Moon
orbits
the Earth
27
The Earth
The Moon
28
The Earth
The Moon
29
On the Moon
NASA pictures
30
Very heavy boots- Why?
 No gravity on the Moon
 Weightless on the Moon
 To stop them floating away
 They weigh very much less than on Earth
 To stop huge bounces
 The Moon’s gravity is very much less than the
Earth’s gravity
31
Weightless?

(NASA pictures)
or are they?
32
apparently weightless
(pictures or animation only –not a demonstration)
33
GRAVITY

Things fall

Things have weight

Things stay in place
34
No Gravity






Would an apple fall?
Would things stay on earth?
What would happen?
What?
Why?
How?