Oct-9-2014 The Mystery of the Magnet

Purpose:
Magnets with same ends behave like springs. They push away from each other. But unlike honest springs, magnets are troublesome and mysterious. They don't behave according to a convenient rule like hooke's law . In comes the students, whose job this time is to find a relationship between the force a magnet exerts and the distance between the magnets.

Lab:
The students will solve the mystery by setting up a system where they can measure the force vs distance of colliding magnets and see if the energy is conserved after collision.
This is done with an air track to create a frictionless surface and a glider with a magnet attached. And a motion sensor.

The air track was put on a slope so that the glider would accelerate toward the magnet. The angle of the slope was recorded.

The angle was changed five times and the experiment repeated. Students used this data to plot force vs distance.

Students used the force vs distance graph to find the relationship of energy of the magnet.

The students then repeated the experiment on a flat angel and a motion sensor to find velocity and position vs time. They used this information to create a graph of the potential and kinetic energies. 

Conclusion

The red in the graph is the total energy and the graph shows that energy was mostly conserved barring air friction.

Oct-7-2014 Is energy conserved?

Purpose:
Students will show that energy is indeed conserved throughout the universe. Or find that it's not and probably win a nobel prize. Students will do this by setting up a system where energy fluctuates between potential and kinetic energy and see if energy is conserved throughout.

The Lab:
Students will attach a mass to a spring that hangs vertically. The mass will then be pulled down by gravity while the elasticity of the spring will pull the mass back up. The energy of the system will then be fluctuating between the gravitational potential energy of the mass/spring, the kinetic energy of the mass/spring, and the elastic energy of the spring.
The students will record of all these changes with a motion sensor and some clever physics calculations. They will add up all the energies to see if the total energy stays constant which theoretically it should barring alien interference.

Here is a picture of the student's heartfelt effort:

Here are the student's calculations:

Elastic PE in spring: 1/2 K (stretch)^2

KE of mass : 1/2mv^2

PE of mass:   mg * y

PE of spring: m(spring) / 2 * g * y + mgh/2  *h  = height of top of spring and y = bottom of spring

KE of spring 1/2 m(spring)/3 * V^2(mass)

GPE: 1/2 m(spring) * g * y (y = bottom of mass height)

The students then used logger pro to graph all of the energy over time. Then the students added all the energies to find the total energy and graphed that. After some clever menagering of the data with the professor's help the students were able to produce a total energy graph that was almost a straight line:

Hint: it's the light green one at the top

Conclusion:

Yay! The experiment was a success! Energy is conserved! All physics is saved!

Oct-2-2014 Observing the relationship between work and energy

Purpose:
Students conducted a lab to observe the relationship between work and energy.

Lab:
We set up a track with a rolling cart with a spring attached. There is a motion sensor on one end and on the other end the spring is attached to a force sensor. We zero both sensors with the spring at rest. Then we turn both sensors on, pull the cart and let go. The varying force and position data is then recorded.

Setup:

Calculations:
The motion and force sensor gave us the data for velocity, force, time and position. Students calculated kinetic energy using the mass and velocity (.5mv^2). Students then plotted a graph of kinetic energy vs position, and force vs position. The students then took the integral of a section of the force vs position graph and compared it to the kinetic energy for the same section. Theoretically the data should be equal. The students found their data to be within reasonable bounds for error.