PhET Motion and Forces simulation

Complete all parts and type your answers in this document. Save (so you can print it out later) and have it printed for Wednesday’s class. It will ultimately be a part of your 2nd quarter journal. If you don’t totally finish, you can hand-write the rest of your answers. But please have a copy of this in class on Wednesday.

Purpose: Toanalyze the effect of applied force and friction (sum = net force) on the motion of an object

Google: PhetRamp Motion and Forces—click on the first hit in the list. Run the Java program (update later, if asked). Click on the tab labeled “Friction”.

  1. For the coefficients of friction initially listed (s = ______; k = ______), calculate the predicted (expected) forces that are necessary to:
  2. start the box in motion:
  1. Keep the box moving at a constant velocity:
  1. Hold the box at rest on the incline:
  1. Do it—check your predictions. (use the playback mode to get the values). What were the forces applied to:
  2. Start the box in motion: ______
  3. Keep the box moving at a constant velocity: ______
  4. Hold the box at rest on the incline: ______
  1. How similar to your measured values are your calculated values?
  1. Predict what a graph of Friction vs. time would look like when you start the box at rest at position -6.0 m, apply a force to start it moving, move it onto the ramp at a constant velocity, then allow it to stop and hold it at rest on the ramp. (sketch your prediction here):
  1. Click on the “Force Graphs” tab, and check the box for “friction”. Sketch the appearance of the graph that appears when you apply a force in the way described in the last question.
  1. Apply a force to the crate to get it moving. As soon as it starts moving, keep pushing with the same applied force. Stop pushing as soon as the crate starts moving up the ramp.
  2. How far up the ramp does the crate slide?
  1. Show calculations, using measurements from within the simulation, to verify this distance. Show your work clearly!
  1. Increase the angle of the ramp. How will this affect how far up the ramp it will slide?
  2. Prediction:
  1. Actual:
  1. Decrease the mass of the box. How will this affect how far up the ramp it will slide?
  2. Prediction:
  1. Actual:
  1. Increase the coefficient of static friction. How will this affect how far up the ramp it will slide?
  2. Prediction:
  1. Actual:
  1. Increase the coefficient of dynamic friction. How will this affect how far up the ramp it will slide?
  2. Prediction:
  1. Actual:
  1. What combination of mass, coefficients of friction, angle, and release point will allow you to push the crate so that it just reaches the top but does not fall off (remove the wall at the top)?
  2. Mass used = ______
  3. Coefficient of static friction = ______
  4. Coefficient of dynamic friction = ______
  5. Angle = ______
  6. Point of release = ______