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# Gravity - a non contact force

Prezi made for a Year 7 science class. Looks at what gravity is, gravitation pull, the difference between weight and mass. It also examines the different rate at which objects fall, as well as terminal velocity - using sky diving as an example
by

## Marta Ivkov

on 17 August 2014

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#### Transcript of Gravity - a non contact force

Contact and Non Contact Forces
A
contact force
is a force that exists between two objects that touch

A
non-contact
force is a force that acts on an object from a distance.

Gravity is a non-contact force
What is gravity?
Gravity is a force of attraction between any two objects

(such as the Earth and a person)
Weight vs Mass
Mass:
Gravity - a non contact force
Gravitational Fields
If an object lies within the Earth's
Gravitational Field
, then gravity will act upon the object.
This is called a
force field
Gravitational Fields
Planets in our solar system lie within the Sun's
gravitational field
.
These planets are therefore pulled towards the sun.
This force is not strong enough to pull plants into the sun, but keeps planets in orbit around the Sun.
Mass is the amount of matter in an object. It would remain the same if you traveled to another planet. Measured in kg/g
Weight vs Mass
Weight
Weight is the pulling force of gravity on an object. It is measured in newtons (N)

Your weight depends on mass and strength of the gravitational field of the planet or moon you are on.

Your weight on the moon is 1/6 of your weight on Earth!
Falling Objects
Why do some objects fall faster than others?

To understand what gravity is

To explore how gravity affects objects on the surface of Earth

To consider how gravity keeps planets in orbit around the sun

To know the difference between weight and mass
Falling Objects
- Because they weigh more than others?
- Because they have a smaller surface area?
- Because of air resistance?
Let's test this out!
1. Time how long it takes for the washer to fall to the ground from a 1.5m drop on its own.

2. Create a device using:
- A plastic bag
- Scissors
- Sticky tape
- String

3. After 20minutes we will compare all groups - the team who gets their washer down at the slowest rate wins a prize!
What happens with no air resistance?
Terminal Velocity
Terminal Velocity is the point at which a falling object falls at a constant speed, because its weight is balanced by air resistance.
If I lived with Martians worksheet!
Calculate your Weight on planets in our solar system!
Sky Dividing Worksheet
Self Reflection
What were today's Learning Goals?

Fill it the self reflection form
Full transcript