1. Complete "When Gravity Gets you down" (Think-pair-share).
Which statements are true?
Jot the answers in your journal.

4. So, Why don’t we stick to each other? Gravity is a weak force!!!
But, gravity does not only pull you down, it attracts all objects with mass inward towards other objects with mass.
So, Why don’t we stick to each other?
Gravity is a weak force!!!

6. Gravity The force of attraction between any two masses
Depends on the masses of the two objects and the distance between them
One of the weakest forces in the universe
Force exerted by every object in the universe on every other object

7. Law of Universal Gravitation
What Newton realized is now called the Law of Universal Gravitation.
The Law of Universal Gravitation states that the force of gravity acts between all objects in the universe.

8. Law of Universal Gravitation
This means that for any two objects in the universe, without exception, attract each other.
You are attracted not only to the Earth but also to all other objects around you.

10. Formula for the Force of Gravity is F=GMm r2
F: Force of Gravity
G: Gravitational Constant (Newton's Constant)
M: Mass of object 1
m: Mass of object 2
r: distance between the centers of the two masses
Use your device to find out the value of the gravitational constant

11. The short version of this formula is that gravity is a force that occurs between two objects and is inversely proportional to the space between their two centers of gravity. So the farther apart they are the smaller the force of gravity is between them. Gravitational force is directly proportional to an object’s mass.

12. Galileo's Famous Experiment

13. NOTE!
The force of gravity is NOT the same as the acceleration DUE to gravity!

14. Some basics… Draw a picture along with each fact to help you remember it!
An object’s mass _______ affect the acceleration of the object due to gravity on earth.
Friction always acts in the _________ direction as motion.
The ___________ of an object will affect the velocity of a free falling object dropping towards earth.
Won’t
opposite
surface area

15. Free Fall
Objects whose only acceleration is due to gravity are in free fall.
Theoretically, objects in free fall continue to accelerate as long as they are falling.
All free falling objects accelerate at the same rate regardless of their mass. (9.8 m/s2)

16. Acceleration of Gravity
Any object which is being acted upon only by the force of gravity is said to be in a state of free fall. There are two important motion characteristics which are true of free-falling objects:
Free-falling objects do not encounter air resistance.
All free-falling objects (on Earth) accelerate downwards at a rate of 9.8 m/s/s (often approximated as 10 m/s/s)

17. If the velocity and time for a free-falling object being dropped from a position of rest were tabulated, then one would note the following pattern.
Time (s) Velocity (m/s)
0 0

18. Air Resistance
Air resistance is an upward force exerted on an object as it falls by air
It is, in essence, a frictional force
For simplicity, the amount of air resistance is determined by two factors
The cross-sectional area of the object
The speed of the object

19. Terminal Velocity
Determine the acceleration of this 85 kg skydiver at points A-D. (Hint: F=ma)
9.8 m/s2
5.68 m/s2
1.56 m/s2
0 m/s2

20. W Richards Worthing High School
Terminal Velocity
Consider a skydiver:
At the start of his jump the air resistance is _______ so he
____ downwards.
zero
accelerates
2) As his speed increases his air resistance will _______
increase
3) Eventually the air resistance will be big enough to _______ the skydiver’s weight. At this point the forces are balanced so his speed becomes ________ - this is called TERMINAL VELOCITY
balance
constant

21. How the forces change with time.
KEY
Gravity
(constant value & always present…weight)
Air resistance
(friction)
Net force
(acceleration OR changing velocity)

22. Terminal Velocity Consider a skydiver:
4) When he opens his parachute the air resistance suddenly ________, causing him to start _____ ____.
increases
slowing down
5) Because he is slowing down his air resistance will _______ until it balances his _________. The skydiver has now reached a new, lower ________ _______.
decrease
weight
terminal velocity

23. Velocity-time graph for the sky diver
Parachute opens – diver slows down
Velocity
Speed increases…
Terminal velocity reached…
On the Moon
Diver hits the ground
New, lower terminal velocity reached
Time

24. Possible Test Questions:
What factor causes terminal velocity to occur?
If an object is at terminal velocity, is it speeding up, slowing down, or falling at a constant speed?
Describe and explain how forces change on a falling object.

25. EXIT TICKET Go back to your answers for "When Gravity Gets you down"
Which statements are true?
Make notes on the ones you missed!