Physics 101: Virtual Lab 4

University of Oregon Department of Physics

• Introduction to Lab

  In this simulation you will be able to control the angle and mass of the cow on both the frictionless roller skates and the one which has a lot of dirt on bearings leading to friction between the skates and the grass incline, upon which the cow is perched.

  A timer counts how long it takes for the cow to reach the bottom of the hill. As the cow slides down the incline, a trail of black dots, each representing one second of motion, will be left behind.

  The two graphs are plotting the X and Y velocities of the cow as a function of time with each dot representing, again, one second of time (note, this timer is not synced to real seconds but runs faster).

• Instructions

  Simply use the sliders to change the angle and change the mass and when you are set, click big red Go button.

  To reset the cow back to its starting position, merely change the angle or the mass. Unfortunately, you can not reset the cow while it is moving - you will have to wait for it to stop at the bottom.

• Experimental Procedure

  select m =100 kg; angle = 45 J; no friction simulation

  1. What is the time it takes for the cow to slide down?
  2. Now change the mass to 20 (the cow will shrink); before hitting the go button write down (in the lab notebook) whether or not you think the time it takes to reach the bottom will change.
  3. Now select the simulation with friction and set m = 100 and angle = 45 and record how long it takes the cow to slide down.
  4. Qualitatively explain why it took longer.
  5. Now change the mass to 20. Write down whether or not you think that changing the mass of the cow, in the case of friction, will alter its travel time.
  6. Change the mass back to 100 and determine the minimum angle that will cause the cow to move.
  7. By determining this minimum angle, state what variable you have measured (refer to the lecture notes on friction)
  8. As the cow slowly rolls down at this minumum angle, watch the behavior of the 4 colored vectors. Explain what these vectors represent.
  9. Finally, inspect the X and Y diagrams and explain why the lines are curved and not straight, as in the case of the 1D cow on skates done in lab 2.

• Lab Notebook Link

  When done, submit your worksheet by clicking on the words "publish to global view" (the first item under reporting tasks).