Lab 4

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.

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.


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)  Click the Playground image.  Explore the interface!

(b)  Design your own frictionless track.  You can ask for some design guidelines in the discussion forum .

(c)  Add friction to your track.


imageOne end of a spring is attached to a rigid support.
Different weights are hung on the other end, and the spring stretches to different lengths.


position (m) force (N)
0.22 0.1
0.255 0.2
image image image image image
image image image image image
image image image    

Add two columns to your spreadsheet.  For each position, enter the elastic potential energy stored in the spring, ½k(x - xequ)2, and the work done by gravity, mg(x - xequ) = F(x - xequ).

position (m) force (N)  ½k(x - xequ)2 (J) mg(x - xequ)  (J)
0.22 0.1    
0.255 0.2    

Gravity does work, converting gravitational potential energy into other forms. 

Convert your log into a lab report.

E-mail address:

Laboratory 4 Report

Save your Word document (your name_lab4.docx), go to Canvas, Assignments, Lab 4, and submit your document.