The Demonstrations

Amazing Crushing Can

The purpose of this demonstration is to show the crushing power of atmospheric pressure. Since we don’t feel the weight of the air above us it is easy to assume that it is actually very small – or hardly even there at all! But really, the reason we don’t feel it is because the pressure inside our body is the same as the atmospheric so when the forces are balanced we do not see or notice any effects.

This experiment is very simple and only requires liquid nitrogen and an empty pop can. At room temperature the can retains its shape, as we hope it would! But when it is cooled with liquid nitrogen the pressure inside the can drops (because of the ideal gas law) and the atmospheric pressure outside the can crushes it. This is a nice visual demo of the strength of atmospheric pressure.

Atmospheric Pressure Model

This model uses ring magnets that are stacked with similar poles facing together on a ring stand. The magnetic force is proportional to the number of magnets above the height from the ground. At the bottom the force is the greatest because there is the greatest number of magnets and at the top it is the least. What is most interesting is the way in which the force decreases as you go up the stand. Amazingly enough, the force per area, or pressure, due to the magnets decreases with height with a very very similar relation to that of atmospheric pressure and height. I have graphed a plot of force (measured in number of magnets) versus height and compared it to a plot of atmospheric pressure versus height in atmosphere. This model gives a visual aid to the understanding of pressure changes with height in the atmosphere.

Coriolis Effect

This demonstration shows the mechanics of the Coriolis force resulting from a rotating reference frame. The clear disk shown is a rotating table whose speed can be changed by increasing and decreasing the voltage on the power supply to the left. There are three different settings for the launcher seen in the middle of the table. Each gives a different speed of the ball that is launched. This allows for us to investigate the effect of both the speed of the ball and the speed of the table on the Coriolis force.

The deflection of the ball is shown by tracing it’s path with paint and then measuring the angular deflection of the ball from what would have been its straight trajectory. These angular displacements can then be plotted against speed to see that the Coriolis force is indeed a true phenomena and also that it is dependent on the speed of ball and the rotating reference frame.

Example Question:
If a jumbo jet is traveling eastward at 200m/s at 30 degrees latitude and applies no force to correct for the Coriolis force, how far will the plane be deflected after one hour?

Answer:

1. Calculate the acceleration:

F=ma=mwvcos(latitude)

a=wvcos(30)

a=(7.27*10^-7 sec^-1)(200m/s)cos30

2. Calculate the deflection:

Vi^2 = Vf^2 + 2ad

D=(Vi^2- Vf^2)/2a

Where vf to the right is equal to:

Vf=Vit + (at^2)/2 where a is calculated above and t=1hr

NEWTON’S LAWS THERMODYNAMICS FORCES IN THE ATMOSPHERE CORIOLIS FORCE STORMS THE DEMONSTRATION HOME

Ó 2004 by Marisa Demers