Free-Fall and Non Free-Fall in The Laws of Motion

What is the definition of Free-Fall ?

The condition of an object when the only force acting on it is gravity (weight)

What forces are present in Free-Fall Conditions ?

Only Gravity no Air Resistance

What two objects accelerate at the same rate regardless of their mass, what to arguments can be made ?

Inertia: If you compare two objects, the more massive objects will have more inertia and therefore resist changes in motion more which results in a smaller acceleration. Weight: If you compare two objects of different masses, the object with more mass is heavier and therefore has more weight, since the only force present in free-fall is gravity, the only force acting on the object is its own weight. Hence, bigger forces accelerate objects more.

Where does the Inertia argument come from ?

Netwons secons law of motion which states that acceleration is inversely proportional to an objects Inertia

Where does the Weight argument come from ?

Newtons secons law of motion which states that acceleration is directly proportional to the net force acting on the object.

Which Vewpoint is correct ?

They both are, they are different aspects of the same problem. The object with more mass has more inertia and therefore resists changes in motion more causing it to have a smaller accelleration. Conversly, the object with more mass has a bigger force of weight acting on it, causing it to accelerate faster. Hence, both effects balance or cancel out making both the objects fall at the same rate.

Since mass is proportional to both Inertia and Weight …

You can’t get more mass without having both Inertia and weight, and they affect the acceleration in opposite ways

If you have Two Rocks, one with 1000 times the mass of the other, what is known about the (Weight) (Inertia)

The object with more mass with have 1000 times the weight and therefore force, but will also have 1000 times the Inertia.

What is the definition of Non Free-fall ?

When objects are allowed to fall and the force of Air Resistance is present.

What two forces act on an object in non free fall ?

Air Resistance and Weight

Given the conditions of Non-Freefall, what should be accounted ?

Net force is now important

In free-fall objects generaly accelerate at ..

Different rates

What object accelerates faster in non Free-Fall conditions ?

Heavier objects fall faster than lighter objects

Define Air Resistance …..

A type of drag force, a force excerted by a fluid on a solid object that is moving through it

The air resitance of an object depends on two things …

The velocity of the object: R congruent to V², the faster an object goes, the more air it hits, the greater R. The Area of the object: Facing the direction of motion, R congruent to A, more area means more air being hit.

What direction is Air Resistance ?

Is directed upwards on a falling object, oppossing its motion

An object Dropped from rest

1. Initially not moving: R and V are equal to zero. The only force present is weight F=W, acceleration=g

2. A short time later: the object is moving slowly, Air resistance is present, the net force is maller (w-R), the accelleration is smaller a<g

3. A longer time later: the object is moving faster, Air resistance is greater, the net force is even smaller, the acceleration is smaller a»g

4. A long time later: The object is moving very fast, the air resistance is know equal to the objects weight, the net force is equal to zero, the acceleration is equal to zero, object falls at a constant velocity and reaches equillibrium.

Define Terminar velovity …

The final, constant velocity that an object in non-free fall achieves when the air resistance is equal to the objects weight.

Parachute …..

A skydiver who has reached terminal velocity then opens the parachute. The increase in area increases the air resistance, which now mist be greater than the weight. The net force and the acceleration are now upwardly directed, and the diver slows down. As he/she slows down, the air resistance decreases until it again equals the divers weight, at a slower terminal velocity.

Why do heavier objects in non free-fall generally fall faster ?

Assume two objects with different weights but equal areas are dropped. They both start to move and they both begin to feel air resistance. But the object with less weight will reach terminal velocity first, and in a short time since the air resistance does not have to be very big for it to equal its weight. So its terminal velocity will be slow. The heavier object must accelerate for more time in order for the air resistance to equal it much larger weight. So its terminal velocity is greater and it falls faster.