gravity. gravity is a pulling force it pulls things down towards the earth
TRANSCRIPT
Gravity
Gravity is a pulling force
It pulls things down towards the earth
Things fall because of gravity
Things always fall down
Gravity was discovered by a scientist called Isaac
Newton
Stories say he discovered Gravity when an apple fell
on his head
What is gravity?
Gravity is the force of attraction between any two objects.
Gravity holds everything and every one on the earth
Even in Australia
In Space, Gravity keeps the planets moving around the
sun
Gravity depends on:
1- Mass of an object
2- distance between objects
Earth’s gravitational acceleration
Try to drop a science book and a paper at the same time, which would hit the ground first????????? (suppose there is no air resistance)
Free falling object would fall with the same acceleration.
Acceleration of gravity is 9.8m/s2
According to Newton’s second law:
Fnet= m x a
What is the force of gravity exerted on an object??
F = m x acceleration of gravity
F= m x g
Application
• What is the gravitational force on an object with a mass of 60 Kg?
• Find the force exerted by a rope on a
10 Kg mass that is hanging from the rope.
Weight
• Does gravity exert a force on you while you are sitting know thinking to find an answer for this question?
• The gravitational force exerted on an object is called weight.
• Because the weight of an object is equal to the Earth’s gravity on the object, weight can be calculated from this equation:
• W = m x g
Application
• On Earth, what is the weight of a large-screen TV that has a mass of 75 Kg
• Find the acceleration of gravity on Mars if a person with a mass of 60 Kg weighs 222N on Mars.
MASS Mass is a physical property of matter that
explains how much matter is in an object
Mass does not change when gravity changes
WEIGHT Weight is a force which is
calculated by multiplying the acceleration of
gravity times mass. Weight can change when
gravity changes
Mass and Weight are two different Properties of Matter
• An elephant on the Earth would weigh less on the Moon, because gravity is less on the moon.
• An elephant’s mass would not change if he went to the moon
WEIGHT