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In what kinds of problems can we use Newton’s 3rd law?

posted Nov 7, 2017, 8:50 AM by Barbara Fortunato
5: M 11/13, 7: M 11/13

Today we will continue studying Newton’s Third Law with some more complex problems. What we must remember about the law is that it says that forces are equal and opposite, but the effects (acceleration) aren’t. The effects of the forces are different, but the forces are the same. Be able to distinguish between something and its effect. 

HandoutTwo Block Problems
Homework: Finish drawing force diagrams for all Two Block Problems and try to finish at least problems 1, 2, and 4.  SOLUTIONS

If you need help remembering how Newton's 3rd Law appears in problems, check out this example:

PhysicsEH: Newton's 3rd Law 2 blocks

Here's another example.  You've done even more complex versions of this with the table top pulley problems:

PhysicsEH: Newton's Third Law tension