Introduction:

Consider dropping a piece paper and a brick from the same height. Although in theory they should both strike the ground at the same time; in practice the brick will always strike the ground first. The reason is because of air resistance. As the paper falls to the ground air resistance is pushing the paper up, this slows the acceleration of the paper.

It is known that as the velocity of an object increases the air resistance acting on the object increases. If we consider jumping out of a plane and free fall towards the Earth the F.B.D. would be as follows:

Now the force of gravity acting on the object does not change, however as we speed up towards the Earth the force of air resistance is increasing. Eventually there reaches a point when the Fg = Fair when this occurs we are no longer accelerating towards the Earth, but fall with a constant velocity that is called the TERMINAL VELOCITY.

The terminal velocity of an object in free fall depends on two main factors: 1. The mass of the object 2. The surface area exposed to the air resistance

For example: A human free falling towards Earth has a terminal velocity of 190 km/h. If you use a parachute the terminal velocity is about 20 km/h.

If we were to observe this motion on a speed time graph it would be as follows:

Notice that the velocity of the object increase until it reaches a constant value which is the terminal velocity. Also notice that the acceleration of the object is NOT CONSTANT, meaning the constant acceleration equations do not apply, but Newton’s second law still does.

Laboratory:

Design a laboratory to determine the proportionality and proportionality constant between the terminal velocity and the mass. You will have available to you coffee filters, meter stick, tape and a stop watch.

You will submit a Laboratory Report including the following sections: