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### Newton's 2nd Law: Multiple Dimensions

• With force in multiple dimensions, we switch to using vectors:
 → Fnet
 =
 m · → a ,
 ⇔
 (Fxnet,  Fynet)
 =
 (m ·ax,  m ·ay).
• We work with each component of the force vector separately. That also means we can break a force vector into its component vectors.
• The normal force is called normal because that means (in math-speak) "perpendicular". A surface can not resist force that is parallel to it.
• If something is on an incline, the portion of gravity that is perpendicular to the surface is cancelled out, but the portion of gravity that is parallel is not.
• Be careful when figuring out how much of the force is parallel! It is very easy to make a mistake and put an angle in the wrong place. Make a diagram and think carefully.

## Newton's 2nd Law: Multiple Dimensions

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