Stuff You Firfot Day Before !

Question 1

Calculating acceleration and momentum

Answer 1

CONSTSNT speed = resuktsnt force 0, so reistsnce =driving force

However when the coupling breaks, the driving force stilk there, but no reistsnce less so there is a resuktsnt firce

Work this out divide by mass to get acceleration and also DRAW A DIAGRAM

Question 2

Momentum has changed, means negative Monteur now?

Question 3

Difference between base units and DERRIVED units?

Answer 3

Base units are those only THOSE THAT ARE BASE UNITS

DERRIVED QUANTITIES IS ANYTHING ELESE THAT IS NOT PAET OF THE 7

Question 4

Prefixes need to know

Answer 4

FEMTO
Pico
Nano
Micro
Mili
Meter
Kilo
Mega
GIGA
Tera
PETA

FEMTO IS -15

Question 5

Car stopping

Answer 5

Thinking and breaking

Thinking is reaction time and speed

Breaking is deceleration deoends on breaks road etc

Question 6

Ways to determine g

Answer 6

Ticker tape connected to a ticker set at specific frequency

Drop mass
And count the dots and multiply by frequency to get time

Now can measure the distance they went for displacement and use suvat where s = 1/2at2
For graph sake can measure s against t2 for different masses I guess

Question 7

Trapdoor

Answer 7

Where electroms get demagnetises drops ball which makes the clock start, and pass a trapdoor disconnect circuit snd time stop

But delay between hitting door, demagnetising

Better to nust use LIGHT GATES

Question 8

Displamcent always

Answer 8

Is the minimum distance between two points straight linen

Question 9

What is the centre of mass thought to be

Answer 9

A point where all mass is concentrated at

But also the point at which if a force is acted through, will only give rise to translational motion and no rotation !!!

Question 10

How to plumb line

Answer 10

Suspend a body using a clamp

Allow it to come to rest, as here itsonly force, weight, will act through its centre of mass, and give rise to no rotational kvoement

Suspend a plumbline which will be the same thing l
And draw and rotate

Question 11

Importsnt about things hanging, why do they come still?

Answer 11

BECAUSE THEIR WEIGHT ACTS THROUGH THEIR COM, GIVING RISE TO NO MOMENT WND THUS NO ROTATION

Question 12

Drag

Answer 12

Is the force that opposes fluids
Determiend in speed and cross sectional area

Can be ignored if order is more than 1000 less
Can’t be when cross sectional area is much more bigger than volume
Or travelling at insane speeds as itsproprtionsl to velocity

Apparently drag to amss

Question 13

Pressure equation

Answer 13

Is given by the total NORMAL FORCE / area

As we normally add up all the normal firces and then divide

Question 14

Assumption to make when calcuaging density if mixtures ,

Answer 14

Find total mass / total volume

And assume that when mixed the moleucles do not react with each cpwhich can affect the densities

Question 15

Pressure in fluids

Change in oressure

What is uothrust?

Answer 15

= dhg

And depends on height if the container that’s it assumign everything else constant

Change in pressure =change in height density x gravity

Ina. Column of liquid there will be different pressures acting at the top of the colourblind compared to the bottom

As a result , p = f/a , f = pa, there will be a difference of f which is = to change in pressure x area

(Newton’s third law causes upthrust , the weight of mass )

Equation is = to change in height x density x gravity x area

Now this is = to the weight if the FLUID DISPLACED as it is the volume x density of fluid

Thus the uothrust acting on an object is = to the eight of fluid displaced

Total pressure = atmospheric and water aswell don’t forgot

So for an object to float its uothrust must = its weight! If it csn’t do that resuktsnt force will always be down so it will just accelerate downwards

But if thrown in where resuktsnt force is something and in water uothust is always greater than object, then now resuktsnt force is up. Thus it will slow down until it monetarily 0 then accelerate up again. In this Tim this is changed by drag

Question 16

Remember fraction of object under water is =

Answer 16

D1/d2
Where d1 is the density of object

As a result the densities are dependent of the ability to float

If density of object is less it will

If not it will fall

Question 17

Definition for work done

Answer 17

1 joule energy needed to move a firce of 1n by 2 m in the direction

So remember work done is force x distance in direction firce is moved

And when we mean firce it can just be the WEIGHT TOO! If you only have that as the force then you are moving this up so be careful

On that note the force done = transferred to gravational store of that thing

So mgh is the same thing is w x d (force x d )

And if firce acted is not same plane then take the component in the same direction of the object thstsbeing moved!

Question 18

Assumption fir gravational potential energy

Answer 18

Is that the grvstsionsl field strength is CONSTSNT at whatever height you go!

Question 19

There we go, what happens if you lower object at same velocity, what happens to GPE

Answer 19

Velocity same, so GpE not Converter to kinetic energy, it instead thermal store of surrounding

But likely at normal times, it convert to kinetic as velocity changes, this happen in rollercoaster

Thus if you know height, you can work out final velocity, assuming that no resistive firces, because then here not all GPE is transferred into KE , but some into other stores

Question 20

Power = fv!

Answer 20

Only can use when in constant velocity !

Because in constant velocity requires a CONSTSNT FIRCE ALONG A DISTANCE

THUS world done = force x distance (as this don’t change)
And in a certain time this jus becomes FV!

Question 21

How to do PAGS

Answer 21

Ideally want a graph based on equation, so if f= kx, then plot F agains X and grsdient K for different values

Then describe experiment with safety featured

Say equipment with lowest uncertainty

Then repeats to make more accurate!!

Question 22

Higher the UTS

Answer 22

The stringer it is

Question 23

How to do PAG young modulus

Answer 23

Yiu can measure force against edge Sion again, thus the gradient is EA/L, which means work out area using average micrometer and length ruler you can work it out

So suspend a wire across length if table cmalling, use a control pulley for fraction set up geniere calliper which is 0.1 easure extension twke safety and you’re goofn

REMEMBER REPEATS !

Question 24

Stress strain for brittle

Answer 24

Never plasticsllt deforms, elastic to properinsk then snaps

Question 25

Why In a wire when deforms the grsdient is still the same?

Answer 25

Because of edtentsion the force is still the same before and after the bonds, like same constants just starting at a different started point

Question 26

How to tell if Newton’s 3rd law not happening

Answer 26

This because they are happening on SAME OBJECT or DIFFERENT FORCE TYPES

Question 27

Principle of conservation of momentum

Answer 27

For a closed system the total momentum in a specified direction is cinserved , unless external forces act upon them

Question 28

How to investigate monetuj

Answer 28

Use air racks to reduce friction as much as possible, then light gates to measure velocities so you have massses and can sxplore monetuj

Elastic when KE conserved
Inelasric si when some Ke transferred to other stores such as heat or sound etc

Energy cinserved overall both times

Monetuj cinserved too

Question 29

Why is total momentum always conserved

Answer 29

In a closed system when an object extends a force to snither object, it enters an equal force l so thst net force in thst direction is ZERO

Thus rate of change of monetuj must be = 0, thus change in momentum is 0 and momentum cinserved

Question 30

Describe accerlwtion using imlukse graph

Answer 30

As f= ma, change in firces also mean acceleration, so if force going up so is acceleration etc

Impulse cinserved because time is constant, however impulse negative direction

Thus if impulse is negative , change of momentum is negative too?

Question 31

P(XUA)

Answer 31

Is the UNION

This is basically EVERYTHING IN VENN DIAGRAM
Including middke
So same as
P of a + p if b
- middle cuz it would count twice

PNA is the INTERSECTION just the middke

Question 32

Probability if bith events occurring? P Na

Answer 32

Is p a x p b

Question 33

What is expected and what is complement

Answer 33

Expected is if oribailty 0,2 and trials 10, thrn 2

Don’t round

Compliment is the OPPSITE

It might be essier to use this if they all are the same, otherwise finding before is hard to go through all combinations

Either an even happens or not
So happening snd comokemtnisith 1- that probability b

Question 34

Probability distribution ?

Answer 34

List all probailties getting Esch case of

And these should add to one

Question 35

Discrete uniform distribution?

Answer 35

Where every falues pro silty can be found and listed

Question 36

How to proves something is idmedpent

Answer 36

Find p a and p b
And p n b
If p a x pi = pnb, then they are independent

Because if a and b independent, probiotics of bith hapepnign si p a x p b

Question 37

Simple random sampling

Answer 37

Every sample I’m the population has same chance of being chosen

Question 38

Cluster sampling

Answer 38

Where population divided into subgroups and tou sample from there

Sample yr 11, can sample yr11s from different schools

Can only happen if this doesn’t change anything, such as the yr 11 doesn’t matter about what school he attends foesntinfluence

Question 39

Poputinu sampling

Answer 39

Sampling somineon the streee

Advantage = quick and easy way to get data
Disadvantage via because sampling someone like at a street for shopping if they there they prolly will etv

Question 40

Statrtificed samplijg

Answer 40

This is where you divide population into categories and start and popeotionsllt sample in Esch group a total amount you want

This is quite rpersentstove however might be hard to split into strata that’s proprtionsl enough for the population!,

Question 41

Quota sampling

Answer 41

This is where you opportunity sample until you get required s,out

Advantage is cheap quick and easy to fill numbers

Dissavantge is gonna be biased

For example interview, people all gonna be there good and you filling numbere

Question 42

Seele selefcted

Answer 42

Opts in

Biased

Question 43

Systematic sampling

Answer 43

Like arrange in random order than pick s certain why before and sample this what

Good representative

Sometimes can’t order and need ti be ordered ifs idling t

Question 44

Categorical data is any

Discrete vs ck tinius

Answer 44

Data that csn’t be used as a numerical value, so even like product codes using numbers are cstgrofisl

Discrete only take certain values

CONTINOUS is a range of vslued

Question 45

Grouping data

Answer 45

Problem is thst raw data is lost (Like actual values)

So stem and leaf is grouped and raw data preserved
Can easily compare find median mode etc
Can interpret trends like median and quartile

Length of line gives shape of each distribution

Can also follow two different sets of data side by side whilst still grouped

Pie chart used for catgeriusl so is bar chart

But pie chart foed prooertionsl so lose data

But scales down to 360 easier tk see side by side

Vertical line großdeutschen don’t confuse the Reede to do with width being cinnected to data. Just a straight line

Question 46

Again why pie chart vs histogram?

Answer 46

Pie chart for discrete and categorical

Histogram for CONTINOUS

Frequency diagram gives kbsurcceed insge thst greater area means more frequency , even tho not the case
(This is when unequal class width used)

As a result you need value thst is constant for area to be proprtionsl.

This is frewuency / class width = rewuency density

So calcite thid by and plot on y axis, then plot frewuency density against clsss width so that frequency is the area

But remember there may be a k factor too, need ti check what is consistent

Question 47

Skewed data

Answer 47

If data is more positive then egwtively skewed, is more negative then positively skewed

If in middle symmetrical

Skewed means less dwindling