Free Fall Review

What is inertia?

Resistance to change in position

Use the terms inertia and force and relate them to acceleration due to gravity

Higher inertia means more resistance to gravity, so it takes more force to move the object. Lower inertia means lower resistance to gravity, so it takes less force to move the object.

What is the value of acceleration due to gravity?

-9.81 m/s² . This means that in one second, velocity changes by -9.81 meters per second

List everything you know about free fall

• inertia resists gravity

• gravity acts the same on objects of different weights

• drag resists gravity

• terminal velocity is when force of drag equals force of gravity

• velocity increases by the same amount for each passing second

  • surface area affects the effect of air resistance

Discuss how objects near the earth fall in the absence of air resistance. Conversely, discuss what happens with air resistance.

without - no drag or inertia, so objects of different weights at extreme heights fall at the same rate

with - objects of higher surface area fall slower than objects with less air resistance (occurs at extreme heights) because of drag and inertia

Galileo’s free fall experiment

He dropped objects of different masses from the Leaning Tower of Pisa and decided they hit the ground at about the same time.

He also dropped balls of different weights down an inclined plane. This showed a slower version of the affect of gravity, taking out the resisting forces and making it easier to see that the objects fell at the same rate

Three men who played a role in our understanding of gravity

UPDATE

Discuss acceleration due to gravity, velocity, mass, and angle

(angle as in an object is falling sideways and not straight down)

The lower the angle, the slower the acceleration and velocity because there is more opposition to gravity

When the angle is 90 degrees, there is less opposition to gravity, so the acceleration and velocity is larger

List the things that must be examined when thinking about the path of an object that has been thrown upward

• length of the base of trajectory

• ascending and descending branches (and the velocities on these branches)

• origin and endpoint (velocity/acceleration at these points)

• force at which the ball has been thrown

  • the time the object is in the air

Compare free fall on earth to free fall in a vacuum

On earth, air resistance opposes gravity, slowing the velocity/acceleration of objects.

In a vacuum, there is no resistance to gravity, so the velocity/acceleration caused by gravity is not affected. Objects with greater surface area fall the same as objects with less surface area (like the feather and the ball example).

Why do objects fall the way they do in a vacuum?

There is no air resistance or other resisting forces opposing the effect of gravity

What is meant by the term “weight” of an object?

Weight is the amount of gravity acting upon a mass

What are the units of weight? Explain

Newtons. 1 N = 1 kg * m/s²

When an object is in free fall with a force acting opposite of it, how must that be handled mathematically? What is the force working in the same direction?

The actual effect of gravity must be calculated because the opposite force “cancels out” some of that gravity. This is called the net force.

The force acting in the same direction is gravity.

Explain and relate mass, inertia, and weight of an object

Mass is the amount of “stuff” in an object. Inertia is resistance to change in position. Weight is the amount of gravity acting on an object.

More mass = more inertia (resistance) = more weight needed to move the object (in a situation with air resistance)

Discuss inertia in terms of a ratio and why all objects fall at the same rate

UPDATE

Draw and label all parts of the path of an object moving up and down. Include all variables that apply and their equivalencies

base of trajectory, origin, ascending branch, apogee, descending branch, endpoint