# PHYS 1110/2020 Midterm 2 Study Guide

## Quick recap of Force Problems

1. Write down knowns + unknowns

2. Draw a picture

3. Choose a coordinate system
+ Usually x is horizontal, y is vertical
+ For ramps choose x to be down the ramp and y to be perpendicular to the ramp

4. Draw a free body diagram!!

5. Write down sum of forces from tree body diagram

6. Is the acceleration in the x or y direction 0?

7. Use force equations to solve for unknowns!

## Work + Energy

Work-Energy Theorem:

“Work done equals change in kinetic energy”

How to calculate work done by forces:

Work done on an object in circular motion is always zero!

Conservation of Energy:

“Energy in the beginning equals energy in the end”
If there’s kinetic and potential at the beginning and only kinetic at the end, then:

Just an example, it won’t always look like this

## Gravity

Force of gravity

If we cross out the little m’s, we get the gravitational acceleration on a planet:

## Momentum

Momentum is ALWAYS conserved!!!

(The lines on top just mean that they’re vectors)

Momentum of one object is

+ Notice that momentum is a vector that points in the same direction as velocity

+ If you want to add two momentums, you have to do vector addition

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