S: Gravity and Acceleration

1
Gravity
Dont let it get you down!
2
Essential Questions

1. Define gravity
2. Explain the law of universal gravitation

3
Aristotle

• Ancient Greece around 400 BC
• He believed that the heavier the object, the
  faster it falls.

4
Galileo Galilei
The Leaning Tower of Pisa
5
What is gravity?
Galileo helped us understand gravity as a force
that exists between the Earth and objects.
Newton showed that the same force exists between
all objects.
Even today, no one knows exactly why objects
attract each other.
6
The Law of Universal Gravitation

• The size of the gravitational force depends on
  two things
• Mass of the objects
• Distance between the objects

7
What is weight?

• Weight is a measure of the gravitational force
  exerted on an object.
• weight is expressed in newtons (N)

8
Elephants feathers

• Objects fall to the ground at the same rate
  because acceleration due to gravity is the same
  for all objects.

9
Air Resistance

• The amount of air resistance depends on the size
  and shape of an object.
• While gravity pulls an object down towards the
  center of the Earth, the air resistance pushes an
  object up from the Earth.

10
Gravity Acceleration

• Objects accelerate towards Earth at
• 9.8 m/s2.
• It is the same for all objects, regardless of
  their mass.

11
Free Fall

• When there is no air resistance, an object is in
  free fall.
• An object is in free fall only if gravity is
  pulling it down and no other forces are acting on
  it.

12
(No Transcript)