Physics › Section C · Forces and Newton's laws › Topic C.5
Problem-solving with Newton's laws
A hanging sign, a cart pulled by a falling mass and two weights over a pulley look like different problems, but they all give way to the same four steps: choose a system, draw its forces, apply Newton's second law along each axis, and check the answer.
In this topic
- Why a routine helps
- Step 1: sketch the problem and choose the system
- Step 2: draw the free-body diagram and pick axes
- Steps 3 and 4: apply the second law, then check
- Worked example: a sign on two cables
- Bodies joined by strings
- Worked example: a cart pulled by a hanging mass
- Worked example: an Atwood machine
- Choosing the system for a contact force
- Common mistakes to avoid
- Key takeaways
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