Hi. Kindly find this ppt which is useful for Cambridge curriculum for year 7 students.

1. INTRODUCTION TO
FORCES
Where do they come from? How are they measured?
How are they added & Subtracted?

2. FORCES ARE
EVERYWHERE
Without forces, sports, dancing, driving…
basically everything would be impossible.
Some forces, like weight, are present when
things are not moving.

3. UNITS
Newton (N)
1 newton = accelerating a 1 kg object at 1 m/s each
second
1 pound = 4.448 newtons

4. FORCES HAVE MAGNITUDE &
DIRECTION
Force is a vector.
That means it has size (magnitude) & direction.
�Magnitude = amount or strength of the force
�Measured in Newtons

5. FORCE VECTORS
A vector is an arrow used to
show the direction & size of a
force.
The arrow points in the
direction of the force.
The length or thickness of
the arrow represents the size
or magnitude of the force.

6. FORCE VECTOR EXAMPLES
A smaller force of 5 N would have a small skinny arrow.
A larger force of 500 N would have either a long arrow or a thick one.
�(yes, this a real image of The Shockwave jet truck traveling at 376 mph
(605 km/h)

7. WEIGHT- THE PULL OF GRAVITY
The Earth’s gravity causes a force that pulls any object downwards.
This force is called weight. Like any force, weight is measured in
newtons (N).
Gravity always pulls you towards the centre of the Earth.
Gravity is a force of attraction between any two objects.
When you draw a force arrow to represent an object’s weight, the
arrow points towards the centre of the Earth.

8. Our weight is caused by the pull of the Earth’s gravity.
An object’s weight is a force acting towards the centre of the Earth.

9. Falling through the floor
The floor pushes upwards on us with a force. This force is called the
contact force.
Any object that you push on pushes back with a contact force.

10. Mass and Weight
When you weigh yourself at home, the scales show the value in kg.
You might say, ‘I weigh 50 kg.’ however, in science, we would say that
your mass is 50 kg.
The mass of an object is measured in kilograms (kg).
The Earth’s gravity pulls on each kg with a force of about 10 N.
1 kg = 10 N
So, if your mass is 50 kg, your weight on Earth is about 500 N.

12. Formation of the Solar System
Where did Solar System Come From?
Scientists can try to solve a problem in two different ways:

13. Facts about the Solar System

19. Movement in Space

23. Speed in Space
Air resistance is like friction. It tends to slow down anything that
is moving.
Air resistance acts in the opposite direction to movement.
The faster an object moves, the greater the air resistance on
the object.
The aeroplane can slow down faster with extra air resistance.
The shape of the wings can be changed to produce extra air
resistance.

24. A space where there are no particles is vacuum.
Earth and the other planets are also moving in a vacuum. This
means there is no air resistance on the planets is from gravity.

25. TIDES

26. What Are Tides?

28. What Causes Tides?
The Moon orbits the Earth.
The Moon stays in orbit because of the force of gravity from the
Earth but the Moon also has gravity, and this gravity pulls on
the Earth.
As the oceans are made from water, the gravity from the Moon
can pull the water more easily than the land.
The pull from the Moon’s gravity is called a tidal force.

30. The side of the Earth closer to the Moon will have high tide.
The Earth takes 24 hours to spin on its axis.
This means that 12 hours later, the side that was closest to the
Moon is now furthest away.
You can see from the drawing that the side furthest away also
has a high tide.
This is why the time between high tides is 12 hours.

31. The Sun also produces a tidal force on Earth, but this is weaker
as the Sun is further away than the Moon.
When the Sun and the Moon are in line with Earth, this
produces a larger tidal force.

32. Effects of Tides?

33. Energy
What is Energy?
Energy is something that must be changed or transferred in order
to do something.
The unit for measuring energy is called joule (J).
Energy Stores and Transfers
There are many different ways in which energy is being stored or
transferred around you all the time.

37. Storing Energy
You can keep uncooked rice for a long time. This is a store of
chemical energy.
Coal and crude oil are stores of chemical energy that formed
millions years ago.
A battery is easy to store chemical energy.
Gravitational potential energy is also easy to store.
Thermal energy (heat) only lasts for a short time. Hot objects
will eventually cool down (they will lose their store of thermal
energy).
Kinetic energy is more difficult than chemical or gravitational
potential energy to store.

38. Changes in Energy
Wood is a store of chemical energy.
Burning the wood changes the chemical energy to thermal
energy (heat).
People are changing chemical energy from their food into kinetic
energy for movement.
The movement is taking the people higher, so kinetic energy is
being changed to gravitational potential energy.

39. There is a process or event that changes or transfers the
energy. For example burning is a process.
Burning changes chemical energy stored in a fuel to thermal
energy.
You can represent the process as arrows and draws diagrams
to show changes in energy.

40. When a book is on the shelf, the book has stored gravitational
potential energy. This energy is changed to kinetic energy as
the book falls.
The energy changes shown in these diagrams are useful
energy changes. That means the energy is changed in a way
that we want.

41. Where Does Energy Go?
Useful and Wasted Energy
A car engine uses the chemical energy stored in the fuel.
this chemical energy from the fuel is also changed into thermal
energy and sound energy.
In fact, only about ¼ or 25% of the chemical energy in the fuel
is used for movement.
The other ¾ or 75% of the energy is wasted energy. This
wasted energy is dissipated and cannot be used again.
Dissipated energy is energy that spreads out where there is no
use for it.