1. Gravity, Weight and Mass
2.3

2. Gravity
Objects at free fall accelerate due to the force of gravity.
Gravity is symbolized by the letter “g” in physics equations.
On Earth, the gravity has a value of 9.8 m/s2
The speed of objects falling in free fall (starting from rest) can be calculated by the formula
v=gt

3. Calculating distance in free fall
To calculate free fall distance use the formula
d=vavgt
However you must make sure that you understand the velocity is an average
(v2 + v1)/2
Since the acceleration of gravity is a constant on Earth, a better formula to use is:
d=v0t +1/2gt2

4. Weight versus Mass
One MAJOR concept to understand in physics is the difference between weight and mass.
Weight is the force that gravity has upon a mass. Weight is a force applied on a mass by gravity. If gravity changes then weight changes.
Mass is the amount of matter (or inertia) in an object. Mass stays the same unless mass is added or taken away.

5. Formula for weight
Weight is symbolized by Fg. This stands for the force of gravity.
Weight can be calculated simply by using the formula
Fg = mg
As weight is a force, it is expressed in Newtons (N). Using the above, mass (kg) times gravity (m/s2) = kg.m/s2 which is equal to a Newton.

6. Air Resistance Why do objects fall at different rates?
Weight? NO
The answer is air resistance. Gravity is not the only force that acts on falling objects. The size and shape of an object affects the rate at which it falls.
Air must move around a falling object. If something delays this action, it will slow the decent of the object due to air resistance.

7. Terminal speed (velocity)
If an object falls long enough, it will reach a point known as terminal speed.
A falling object continuously accelerates each second. As it accelerates, air must be moved out of the way faster to make way for the falling object.
This creates a kind of friction between the object and the air.
Eventually, the air resistance will become so great that it will cancel out all acceleration due to gravity and the object will travel at a constant rate known as terminal speed.