Part I: Free-Body Diagrams

Free-Body 1x Free-Body 2x Free-Body 3x Free-Body 4x
Free-Body 1y Free-Body 2y Free-Body 3y Free-Body 4y

Please wait for the animation to completely load.

An 8-kg block is pushed across the floor (position is given in centimeters and time is given in seconds).  Push "play" and let the animation run.  Restart.

  1. Describe the motion.
  2. Sketch a possible free-body diagram for the block.
  3. What is the velocity of the block at t = 2-seconds?  Show your work.
  4. What is the velocity of the block at t = 4-seconds? Show your work.
  5. What is the acceleration of the block?  Show your work.
  6. Therefore, the net force in x-direction equals?
  7. Net force in the y-direction?
  8. Consider the forces in the x-direction (horizontal forces).  Click each of the four possible diagrams.  The length of the vector represents the magnitude of the force.  Only one is a possible free-body diagram.  For each animation, indicate why it is or is not a possible force diagram.
  9. Based on this, sketch a complete free-body diagram.
  10. Explain any differences with your original sketch.
  11. Click on the complete free-body diagram animation below. 

  1. Does is agree with your sketch above? If not, explain why the animation (and not your drawing) shows the correct free-body diagram.

Note that in this case, there is a frictional force, but the form of the frictional force will be addressed later in this course.


Original problem and script: Illustration 4.2, Physlet Physics
2004 by Prentice-Hall, Inc. A Pearson Company