Gravity

Question 1

What are the four fundamental force of nature?

Answer 1

1: Gravity
2: Electromagnetism
3: The Strong Nuclear Force
4: Th Weak Nuclear Force

Question 2

What is the first Keppler’s law of planetary motion?

Answer 2

the orbit of a planet is an ellipse with the Sun at one focus
perihelion - aphelion

Question 3

What is the second Keppler’s law of planetary motion?

Answer 3

an imaginary line joining the Sun and a planet sweeps out equal areas in equal times
so planets move faster when they are closer to the sun

Question 4

What is the third Keppler’s law of planetary motion?

Answer 4

Harmonic Law: The further a planet is from the Sun, the longer it takes to orbit!
P*2 = a*3
where:
P = orbital period (Earth years)
a = average distance from Sun (AU)

Question 5

What is the first Newton’s law of motion?

Answer 5

An object will remain at rest or move in a straight line at constant speed unless a force acts
Conclusion: Since the planets are clearly not at rest or moving in straight lines, but moving in ellipses, a force must be acting!
This force is called gravity!

Question 6

What is the second Newton’s law of motion?

Answer 6

F = ma
where:
F = force applied
a = resultant acceleration
m = mass

Question 7

What is the third Newton’s law of motion?

Answer 7

Action and reaction are equal and opposite!

Only applies to forces that are in equilibrium (balance)

Question 8

What is Newton’s universal law of gravitation?

Answer 8

F=(G.M1.M2)/d*2
The closer a planet is to the Sun the stronger the force of gravity!
The stronger the force of gravity the larger the acceleration!