# Kinematics - M1 Watch

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The book doesnt really tell you what exactly the following formulae is used for - only how to derive it:

Can someone please enlighten me

TIA

**v^2 = u^2 + 2as**Can someone please enlighten me

TIA

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#2

Its one of the equations of motion.

There are 4 i think:

v^2=u^2 + 2as

s=ut +(1/2)at^2

s=(1/2)(u+v)t

v=u+at

v is final velocity

u is initial velocity

s is displacment (distance from start)

a is acceleration (UNIFORM)

t is the time

They are used in M1 and M2 for basic acceleration questions and projectile questions.

Note. Projectiles have 2 components up or down / left or right.

There are 4 i think:

v^2=u^2 + 2as

s=ut +(1/2)at^2

s=(1/2)(u+v)t

v=u+at

v is final velocity

u is initial velocity

s is displacment (distance from start)

a is acceleration (UNIFORM)

t is the time

They are used in M1 and M2 for basic acceleration questions and projectile questions.

Note. Projectiles have 2 components up or down / left or right.

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(Original post by

Its one of the equations of motion.

There are 4 i think:

v^2=u^2 + 2as

s=ut +(1/2)at^2

s=(1/2)(u+v)t

v=u+at

v is final velocity

u is initial velocity

s is displacment (distance from start)

a is acceleration (UNIFORM)

t is the time

They are used in M1 and M2 for basic acceleration questions and projectile questions.

Note. Projectiles have 2 components up or down / left or right.

**Syncman**)Its one of the equations of motion.

There are 4 i think:

v^2=u^2 + 2as

s=ut +(1/2)at^2

s=(1/2)(u+v)t

v=u+at

v is final velocity

u is initial velocity

s is displacment (distance from start)

a is acceleration (UNIFORM)

t is the time

They are used in M1 and M2 for basic acceleration questions and projectile questions.

Note. Projectiles have 2 components up or down / left or right.

I know you can use the formula v=u+at and then rearrange that to find just about anything, from velocity to initial velocity , to acceleration to time - except of course the displacement which is found via

**s=ut+1/2at^2**. I am just a bit confused because if you can use v=u+at to find all what I have mentioned then what is the point of

**v^2=u^2 + 2as**...

Thank you v much for helping me get to grips with mechanics! Its all v interesting btw.

P.S.

Will the formula booklets in the exam have any of the formulas for MEchanics listed in there?

Thanks again!

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#4

Nope... from what i remember. None of the linear acceleration equations are in the F/B.

There are 4 different formular because u may not have all of the information u need.

When i do an uniform acc Q. I ALWAYS write

s=

u=

v=

a=

t=

then read the question and fill them in. Look whats missing, and see what i have to find.

E.g.

A car passes A at 10ms^(-1) and accelerates at a constant rate of 5ms^(-2). It passes the finish line B which is 1km from A. How fast was the car going when it crossed the finish line.

s= 1000

u= 10

v = ?

a = 5

t = / (not required)

v^2 = u^2 + 2 a s

v = sqrt(10^2 + 2 * 5 * 1000)

This is jus one off top of my head so i aint gonna work it out lol

Hope this helps.

There are 4 different formular because u may not have all of the information u need.

When i do an uniform acc Q. I ALWAYS write

s=

u=

v=

a=

t=

then read the question and fill them in. Look whats missing, and see what i have to find.

E.g.

A car passes A at 10ms^(-1) and accelerates at a constant rate of 5ms^(-2). It passes the finish line B which is 1km from A. How fast was the car going when it crossed the finish line.

s= 1000

u= 10

v = ?

a = 5

t = / (not required)

v^2 = u^2 + 2 a s

v = sqrt(10^2 + 2 * 5 * 1000)

This is jus one off top of my head so i aint gonna work it out lol

Hope this helps.

0

(Original post by

Nope... from what i remember. None of the linear acceleration equations are in the F/B.

There are 4 different formular because u may not have all of the information u need.

When i do an uniform acc Q. I ALWAYS write

s=

u=

v=

a=

t=

then read the question and fill them in. Look whats missing, and see what i have to find.

E.g.

A car passes A at 10ms^(-1) and accelerates at a constant rate of 5ms^(-2). It passes the finish line B which is 1km from A. How fast was the car going when it crossed the finish line.

s= 1000

u= 10

v = ?

a = 5

t = / (not required)

v^2 = u^2 + 2 a s

v = sqrt(10^2 + 2 * 5 * 1000)

This is jus one off top of my head so i aint gonna work it out lol

Hope this helps.

**Syncman**)Nope... from what i remember. None of the linear acceleration equations are in the F/B.

There are 4 different formular because u may not have all of the information u need.

When i do an uniform acc Q. I ALWAYS write

s=

u=

v=

a=

t=

then read the question and fill them in. Look whats missing, and see what i have to find.

E.g.

A car passes A at 10ms^(-1) and accelerates at a constant rate of 5ms^(-2). It passes the finish line B which is 1km from A. How fast was the car going when it crossed the finish line.

s= 1000

u= 10

v = ?

a = 5

t = / (not required)

v^2 = u^2 + 2 a s

v = sqrt(10^2 + 2 * 5 * 1000)

This is jus one off top of my head so i aint gonna work it out lol

Hope this helps.

s=

u=

v=

a=

t=

I will remember that.

In the M1 book , page 40 example 3 they used the above formula for retardation, so I am wondering if it is only specifically for that.

Oh yes, do the earlier chapters get easier as you go through the later chapters?

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#6

All the equations can be used for retardation.

Just put a = (-)5ms^(-2) (negative acceleration)

Yeah its the same with everything, the more u do the easier it is to do.

The uniform acceleration questions will be v.easy once uve done the chapter.

Just basically remember suvat and the formula for them and ur sorted basically.

Just put a = (-)5ms^(-2) (negative acceleration)

Yeah its the same with everything, the more u do the easier it is to do.

The uniform acceleration questions will be v.easy once uve done the chapter.

Just basically remember suvat and the formula for them and ur sorted basically.

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(Original post by

All the equations can be used for retardation.

Just put a = (-)5ms^(-2) (negative acceleration)

Yeah its the same with everything, the more u do the easier it is to do.

The uniform acceleration questions will be v.easy once uve done the chapter.

Just basically remember suvat and the formula for them and ur sorted basically.

**Syncman**)All the equations can be used for retardation.

Just put a = (-)5ms^(-2) (negative acceleration)

Yeah its the same with everything, the more u do the easier it is to do.

The uniform acceleration questions will be v.easy once uve done the chapter.

Just basically remember suvat and the formula for them and ur sorted basically.

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#8

(Original post by

What is the hardest chapter...warn me now!!!! so I am prepared! Surely there cant be anything as bad as Vectors in this whole book.

**DOJO**)What is the hardest chapter...warn me now!!!! so I am prepared! Surely there cant be anything as bad as Vectors in this whole book.

2 body's connected by an inextensible string. one hanging off the table. when its dropped blah blah

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#9

It is useful to have all 5 formulae as you will notice that each one omits one variable.

The derivations are straight forward:

Begin with

Consider a v-t graph consisting of a constant acceleration (straight diagonal line) from, say, 0 to 20ms^-1.

You can appreciate that dist. = area under line

-->

Now: t = 2s/(v + u) = (v - u)/a

So:

And: v = u + at = 2s/t - u

So:

And: u = v - at = 2s/t - v

So:

The derivations are straight forward:

Begin with

*v = u + at*Consider a v-t graph consisting of a constant acceleration (straight diagonal line) from, say, 0 to 20ms^-1.

You can appreciate that dist. = area under line

-->

*s = 1/2(v + u)t*Now: t = 2s/(v + u) = (v - u)/a

So:

*2as = v^2 - u^2*And: v = u + at = 2s/t - u

So:

*s = ut + (1/2)at^2*And: u = v - at = 2s/t - v

So:

*s = vt - (1/2)at^2*
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