4.1

Newton's Second Law

Student Notes

You will explore Newton's second law, or SF=ma, in this simulation.
A block is resting on a frictionless surface. Up to three horizontally-directed forces can be applied to the block. The block always starts from rest. When you click the run button, the motion of the block is calculated and shown in the animation.
First, with only one force on the block, how will the block move? Predict the shape of the distance and velocity graphs for motion with one constant force. Set force 1 to 5 N, set the other two forces to zero, and run the simulation to check your prediction.
How will doubling the force change the motion and the graphs? Make a prediction, and set force 1 to 10 N. Use the simulation to check your prediction.
Would the motion be any different if two +5-N forces acted on the block instead of a single 10-N force? Set force 1 to 5 N and set force 2 to 5 N. Compare the acceleration of the block to the previous case with a single 10-N force.
What would happen if force 2 is still 5 N in magnitude, but is directed to the left? We can signify this as -5 N. Set force 2 to -5 N, and run the simulation to see what happens.
Forces 1 and 2 are said to cancel, since their sum is zero. Both forces are still present, however.
The mass is the proportionality constant in Newton's second law between the net force and the resulting acceleration. Predict what would happen to the acceleration if the mass is doubled. Use the simulation to check your prediction using one non-zero force.

Self-test

Set force 1 to 10 N, force 2 to -5 N, and force 3 to 5 N. Set the mass to 1 kg. Predict the acceleration, and test it with the simulation.

Copyright © 2006 John Wiley & Sons, Inc. All rights reserved.