Operational Definition of Force

Velocity Acceleration

Mass of the cart, m= kg.

Although most physics would agree that force is not as fundamental as a conservation law, it is still considered central to the study of physics.  A force is a push or a pull,  that is an interaction, exerted by one object on another object.  We know from experience that a push or a pull often causes an object to move.  This allow us to quantify the definition of force in terms of a quantity that was defined previously, momentum.

The magnitude of a force exerted on an object is given by the time rate of change that the force causes on the objects momentum.

Use this definition to do the following exercise.  Set the mass in the text box before you select the graph type, velocity or acceleration.


The 1.0 kg cart in the simulation interacts with the two-handed image if the image is near the left-hand or right-hand side of the cart.  The arrow below the cart shows the direction and strength of the interaction. You will have to move the image to keep it in front of the cart since the interaction changes direction if the cart passed through the center of the image. Start the simulation and do the exercise.  Assume MKS units.  Reset the animation if the cart goes off the end of the track.

  1. Drag the "handy" image to the left of the cart and and keep dragging it to the right as the cart moves.  Describe the resulting velocity graph.
  2. Repeat (a) if the image is to the right of the cart.
  3. What force does the image exert on the cart if it is to the left of the cart?
  4. What force does the image exert on the cart if it is to the right of the cart?
  5. What changes on the velocity graph if the mass of the cart is doubled or decreased by a factor of two?
  6. Drag the image to the left of the cart and and keep dragging it to the right as the cart moves.  Describe the resulting acceleration graph.
  7. Repeat (f) if the image is to the right of the cart.s
  8. What changes on the acceleration graph if the mass of the cart is doubled or decreased by a factor of two?

Production notes and screen shots:

Reference:

Newton's second law.

See Mazur, Principles Volume Ch 9.s

Answers

  1. The velocity graph has a constant positive slope of 0.2 m/s2. 
  2. The velocity graph has a constant negative slope of -0.2 m/s2. 
  3. |F| = 0.2 N.  to the right.
  4. |F| = 0.2 N.  to the left.
  5. The slope is inversely proportional to the mass.
  6. The acceleration is roughly constant with a value of a= +0.2.
  7. The acceleration is roughly constant with a value of a= -0.2.
  8. the acceleration is inversely proportional to the mass.

Credits:
Problem by Wolfgang Christian
Script by Wolfgang Christian