Free Fall and Air Resistance
Computer drawing of a falling ball ubject to gravitational and drag forces. D is equal to a drag coefficient Cd times one half the air density r times the velocity V. Before we can discuss how air resistance (often called a drag force) affects The relationship between air resistance force and velocity is not. Air resistance is also called as “ drag “ The velocity of a object moving through air is given by V = Square root (2W/Cd p A) Where W is weight of the object, Cd is.
Objects that are said to be undergoing free fall, are not encountering a significant force of air resistance; they are falling under the sole influence of gravity.
Under such conditions, all objects will fall with the same rate of acceleration, regardless of their mass. Consider the free-falling motion of a kg baby elephant and a 1-kg overgrown mouse.
- Free Fall and Air Resistance
- The dependence of air resistance on velocity
If Newton's second law were applied to their falling motion, and if a free-body diagram were constructed, then it would be seen that the kg baby elephant would experiences a greater force of gravity. This greater force of gravity would have a direct effect upon the elephant's acceleration; thus, based on force alone, it might be thought that the kg baby elephant would accelerate faster. But acceleration depends upon two factors: The kg baby elephant obviously has more mass or inertia.
This is true even if one or both of the objects is a fluid a gas or liquid, such as air or water.
PhysicsLAB: Air Resistance: Terminal Velocity
When the fluid in question is air, the friction force generated is called air resistance or wind resistance. How does friction, and in particular, air resistance work? Well, nobody really knows - it is an active and important area of research.
Friction forces in general, and air resistance forces in particular, are very complex.
We do know that it is impossible to make simple, accurate, theoretical statements about air resistance. On the other hand, if you are willing to not take them too literally and carry them too far The air fluid resistance force on an object depends primarily on: The word "relative" is important here - as far as the force is concerned, it doesn't matter if the object is moving and the air or other fluid is at rest, or if the air is moving and the object is at rest, or whatever.
However, some other sources suggest that at low speeds, the air resistance grows linearly with velocity: Your job today is to figure out which of these formulae more accurately fits the data from a simple experiment.
The experiment Create a set of objects with the same size and shape, but different mass, by stacking coffee filters: Try using stacks of 2, 4, 6, 8, 10 filters. Write your name and the number of filters on the inner bottom surface of each stack. Give the objects what we HOPE will be terminal velocity by having one team member stand on the third floor of the atrium and drop the stacks, one at a time.
After a short acceleration, each one will we hope reach a constant speed for the majority of its fall. Have a second team member stand at the bottom of the atrium and measure the time it takes for each stack to fall from the level of the carpet on the first floor to the bottom of the atrium.
Make two trials for each stack. Calculate the speed of each stack during this final portion of its flight; the distance from atrium floor to first-floor carpet is 4. Compare your results to those of other groups.Misconceptions About Falling Objects