Flashcards in Physics Class 2 Deck (26)

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1

##
If circumference increases, what happens to:

1) Time?

2) Speed?

###
Time is the same

Speed increases too

2

## With uniform circular motion, is speed and velocity constant?

###
Speed is consttant

Velocity is not

3

## Centripetal acceleration

### Ac = v^2 / r

4

## Centripetal Force

### Fc = (mv^2)/ r

5

## Forces that act perpendicular to velocity _____ the speed, but ______.

###
Cannot change the speed

but can change direction

6

## Torque

### Force's effectiveness at making an object spin/rotate

7

## Torque formula

###
τ = rFsinθ

Units: N X m

Torque is maximized with sin90

OR (if you're able to determine the lever arm):

τ = lF

l = rsinθ

8

## In static equilibrium, what is the net torque and net force?

### 0 because it is motionless

9

## What does 'static equilibrium mean'?

### Motionless, no net torque

10

## Lever arm

### shortest distance from the pivot to the line of action of the force

11

## Fulcrum

### Part that never moves

12

## Work

###
Measures how much force contributes to the displacement of an object

W = Fdcosθ

Units: N x m --> Joules

- can be positive, negative or 0

13

## When is work +, - or 0

###
Positive Work

0 < θ <90

Zero Work

θ = 90

Negative Work

90 < θ < 180

14

## Conservative Forces

###
Gravity

- what goes in, comes out

15

## What does work done by gravity depend on?

### Initial and final height, does not matter about path taken to reach those heights

16

## Power

###
Rate at which work is done

Formula:

P = W/t

Units: J/s --> N x m / s --> W (watts)

17

## Power for a constant force parallel to a constant velocity

###
P = Fv

* v = d/t

18

## Kinetic Energy

###
Ability to do work

Formula: 1/2 mv^2

Units: kg x (m/s)^2 = J

19

## Total work done if no change in other forms of energy...

###
Wtotal = ΔKE

If work is positive = gains KE

If work is negative = loses KE

If work is 0 = speed is constant

20

## Work done by gravity

###
Wgravity = mgh

= -ΔPE (losing PE, gaining KE)

21

## Wgravity = -ΔPE (losing PE, gaining KE)

### In any spontaneous process, potential energy decreases

22

## When only conservative forces are doing work...

### KEi + PEi = KEf + PEf

23

## Conservative vs Non-Conservative forces

###
KEi + PEi + Wnc = KEf + PEf

Wnc = ΔE

Conservative:

- gravity, electrostatic force, spring force

- have PE associated with them

- if they're the only forces doing work, mechanical energy is conserved

Non-conservative forces:

- kinetic friction, drag

- always do negative work

- if they're doing work, mechanical energy is not conserved

24

## Simple machines

###
Reduce the amount of force required to do something

1. Pulleys

2. Inclined Planes

25

## Mechanical Advantage

###
Factor by which force can be reduced when using a simple machine

MA = Fresistance / Feffort

= normal / with machine > 1

Mechanical advantage > 1 because reducing amount of force by increasing displacement. Work stays the same

F = mg ---------------------> F = mgsinθ

d = h ------------------------> d = h / sinθ

W = mgh -------------------> W = mgh

26