Studio Session 5

Work and Energy

Energy conservation for an isolated system is a fundamental principle of physics.  Energy for an isolated system is always conserved.  It may change forms, but the total amount of energy in an isolated system is constant.  Energy can, however, be converted from one form to another form.  Work is the conversion of one form of energy into another.  Energy comes in different forms, kinetic energy, potential energy, chemical energy, thermal energy, etc.  If an object has energy, it has the potential to do work. 

There are several forms of potential energy.  Kinetic and potential energy are called mechanical energy or ordered energy.  Thermal energy is disordered energy.  Friction converts mechanical energy into disordered energy.
When no disordered energy is produced, then mechanical energy is conserved.

Today we will track the mechanical energy in various systems and explore the relationship between work and energy.

Equipment needed:

How does the motion sensor work?

An electrostatic transducer in the face of the Motion Sensor transmits a burst of 16 ultrasonic pulses with a frequency of about 49 kHz.  The ultrasonic pulses reflect off a target and return to the face of the sensor.  The target indicator flashes when the transducer detects an echo.

The sensor measures the time between the trigger rising edge and the echo rising edge. It uses this time and the speed of sound to calculate the distance to the object. To determine velocity, it used consecutive position measurements to calculate the rate of change of position. Similarly, determines acceleration by using consecutive velocity measurements.

Note:  The motion sensor must face the target.

Open a Microsoft Word document to keep a log of your experimental procedures and your results.  This log will form the basis of your studio session report.  Address the points highlighted in blue.  Answer all questions.  Include the information that your answers are based on.

Experiment 1

In this experiment you will do work compressing a spring.  You will then let the spring do work converting elastic potential energy into gravitational potential energy.

Experiment 2

In this experiment you will lift one end of the track.  You will then measure the conversion of gravitational potential energy into kinetic energy.



Use an on-line simulation from the University of Colorado PhET group to track mechanical energy in a skate park.
Link to the simulation:

(a)  Explore the interface!

(b)  As a group, design your own frictionless track.  You session instructor will give you some design guidelines that you should follow.

(c)  Add friction to your track.

(d)  Optional:  Move the skater to a different planet or to free outer space.

Convert your log into a session report, certify with you signature that you have actively participated, and hand it to your instructor.