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| 184_notes:force_review [2023/08/17 18:55] – [Types of Forces] tdeyoung | 184_notes:force_review [2023/08/18 14:04] – [Common Mistakes] tdeyoung |
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| ==== Common Mistakes ==== | ==== Common Mistakes ==== |
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| | * **Not bothering draw a free-body diagram** to keep track of the different forces, which object they act on, and which direction they push. This is a great way to get confused, and often leads to the next error: |
| * **Adding the magnitudes of forces together**, as if they were plain numbers instead of vectors. This gives you the correct result __only__ if the forces point in the same direction. Usually, you need to add forces together component by component. | * **Adding the magnitudes of forces together**, as if they were plain numbers instead of vectors. This gives you the correct result __only__ if the forces point in the same direction. Usually, you need to add forces together component by component. |
| * **Assuming the force on an object has a constant magnitude**. Sometimes forces __are__ constant, like gravity near the Earth's surface, and in those situations you can use tools like the kinematic equations ($x_f = \tfrac{1}{2}a (\Delta t)^2 + v_0 (\Delta t) + x_0$ and so on). But often the magnitude or direction of a force changes during a problem, like with springs, and then you //can't// use these equations. | * **Assuming the force on an object has a constant magnitude**. Sometimes forces __are__ constant, like gravity near the Earth's surface, and in those situations you can use tools like the kinematic equations ($x_f = \tfrac{1}{2}a (\Delta t)^2 + v_0 (\Delta t) + x_0$ and so on). But often the magnitude or direction of a force changes during a problem, like with springs, and then you //can't// use these equations. |