Flashcards in Physics Class 1 Deck (12)

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1

## Newton's First Law

###
Law of inertia

- an object in motion tends to stay in motion

- an object at rest tends to stay at rest

- velocity only changes with an applied net force

2

## Newton's Second Law

###
Fnet = m a

Force ∝ a

3

## What does it mean if Fnet = 0

### Velocity is not 0 too, it just means velocity is constant

4

## Weight formula

### W = m g

5

## Newton's Third Law

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For every action there's an equal & opposite reaction

- do not cancel out

- equal in magnitude and opposite in direction

6

## Normal force

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force a surface exerts to keep itself intact

- direction is normal (perpendicular) to surface

7

## Kinetic friction vs static friction

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Kinetic friction

Fk = μk Fn

Use: skidding or slipping

- Direction opposes velocity

Static friction

Fs μs Fn

Use: no motion relative to contact surface or rolling without slipping

- Direction opposes other forces

8

## How to know to use μk or μs

###
1. Find Fsmax ---> μs x Fn

2. Does Fapplied > Fsmax? If yes, use μk because there will be slippage, if not then Fs = Fapp

If yes...

3. Use kinetic friction formula to find the force of friction (Fk = μk x Fn)

* Fn will be in the x direction

9

## Force of tension

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Always directed along the rope, away from object it's connected to

- tension is same throughout any single rope

10

## How to calculate acceleration of masses?

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1. Set a positive direction of rotation for pulley

2. Determine net force acting on system of masses (tensions cancel out)

3, aooky Fnet = mtotal x a

11

## An object undoing nonzero acceleration is...

###
- turning at constant speed

- slowing down

- speeding up

12