Mathematics Clan! Options

[jd1478jd]

Here's a little, very simple question for you lot;

An article states that the Earth will always make a complete revolution every twenty four hours.

Please prove that in order for this to be correct, the Earth must rotate at 1/4 degrees per minute.

Here is a slightly harder question;
If a car brakes suddenly, there is a possibility that the vehicle will skid. Accident investigators use a formula in order to determine the velocity of the vehicle; v^2=Mu * D

Where D is the distance in metres of the skids that were made, and mu is the coefficient of friction between the tyres and the surface. (This value is variable, and entirely dependant on the surface of the road and the tyres used.)

In a 30mph speed zone, an accident occurs, and so causes skids of 28 metres in length. The investigators perform an experiment and find out that a car travelling at 10 metres per second, leaves skid marks of length 17.5 metres.

Use this data to find the value of mu. (Assume that the tyres used in the experiment were identical to those of the car in the accident.)

Also, find the velocity of the car (In mph) when the brakes were applied.
Assume that 1 mph = 0.447 metres per second.

Good luck!!

This post has been edited by jd1478jd: Jan 6 2006, 10:03 AM

[changalator]

This is the type of thread that supports negative asian sterotypes.

[stillarook]

Here's a little, very simple question for you lot;

An article states that the Earth will always make a complete revolution every twenty four hours.

Please prove that in order for this to be correct, the Earth must rotate at 1/4 degrees per minute.

Here is a slightly harder question;
If a car brakes suddenly, there is a possibility that the vehicle will skid. Accident investigators use a formula in order to determine the velocity of the vehicle; v^2=Mu * D

Where D is the distance in metres of the skids that were made, and mu is the coefficient of friction between the tyres and the surface. (This value is variable, and entirely dependant on the surface of the road and the tyres used.)

In a 30mph speed zone, an accident occurs, and so causes skids of 28 metres in length. The investigators perform an experiment and find out that a car travelling at 10 metres per second, leaves skid marks of length 17.5 metres.

Use this data to find the value of mu. (Assume that the tyres used in the experiment were identical to those of the car in the accident.)

Also, find the velocity of the car (In mph) when the brakes were applied.
Assume that 1 mph = 0.447 metres per second.

Good luck!!

please, i'm a middle schooler, not some math geek in a university

[Takashi]

please, i'm a middle schooler, not some math geek in a university

I'll join.
You don't need to be in university to answer those questions

Question
An article states that the Earth will always make a complete revolution every twenty four hours.

Please prove that in order for this to be correct, the Earth must rotate at 1/4 degrees per minute.

My Solution
24 hours = 1440 minutes
Full rotation = 360 degrees
360/1440 = 0.25 degrees per minute

Question
If a car brakes suddenly, there is a possibility that the vehicle will skid. Accident investigators use a formula in order to determine the velocity of the vehicle; v^2=Mu * D

Where D is the distance in metres of the skids that were made, and mu is the coefficient of friction between the tyres and the surface. (This value is variable, and entirely dependant on the surface of the road and the tyres used.)

In a 30mph speed zone, an accident occurs, and so causes skids of 28 metres in length. The investigators perform an experiment and find out that a car travelling at 10 metres per second, leaves skid marks of length 17.5 metres.

Use this data to find the value of mu. (Assume that the tyres used in the experiment were identical to those of the car in the accident.)

Also, find the velocity of the car (In mph) when the brakes were applied.
Assume that 1 mph = 0.447 metres per second.

My Solution
v^2 = muD (mu is coefficient of friction)
10^2 = 17.5mu
100/17.5 = mu
therefore mu = 5.714 to 3 d.p.

Accident that takes place:
v^2 = 5.714*28
v^2 = 160 (using unshortened value of mu)
therefore v = 12.65 m/s to 2 d.p. which is 28.3 mph to 1 d.p.

Haven't checked it through, think it's ok though, might be some typos

[yee~hah]

ugh! i hate math.. LOL..

math is my worst nightmare!!!

[changalator]

ugh! i hate math.. LOL..

math is my worst nightmare!!!

Me too, math is too complex.

[yee~hah]

^^ yeah... and all those math-know-it-alls are annoying...LOL.. just kidding.. but i wish that i was a math whiz....LOL..

[jd1478jd]

Maths is only annoying if you can't see the root or escence of the puzzle, in exactly the same way as english is boring to us lot.

[Takashi]

^ So what were the answers?

[stillarook]

^ So what were the answers?

absolutely no idea at ALL.

[jd1478jd]

I'll join.
You don't need to be in university to answer those questions

Question
An article states that the Earth will always make a complete revolution every twenty four hours.

Please prove that in order for this to be correct, the Earth must rotate at 1/4 degrees per minute.

My Solution
24 hours = 1440 minutes
Full rotation = 360 degrees
360/1440 = 0.25 degrees per minute

Question
If a car brakes suddenly, there is a possibility that the vehicle will skid. Accident investigators use a formula in order to determine the velocity of the vehicle; v^2=Mu * D

Where D is the distance in metres of the skids that were made, and mu is the coefficient of friction between the tyres and the surface. (This value is variable, and entirely dependant on the surface of the road and the tyres used.)

In a 30mph speed zone, an accident occurs, and so causes skids of 28 metres in length. The investigators perform an experiment and find out that a car travelling at 10 metres per second, leaves skid marks of length 17.5 metres.

Use this data to find the value of mu. (Assume that the tyres used in the experiment were identical to those of the car in the accident.)

Also, find the velocity of the car (In mph) when the brakes were applied.
Assume that 1 mph = 0.447 metres per second.

My Solution
v^2  = muD (mu is coefficient of friction)
10^2 = 17.5mu
100/17.5 = mu
therefore mu = 5.714 to 3 d.p.

Accident that takes place:
v^2 = 5.714*28
v^2 = 160 (using unshortened value of mu)
therefore v = 12.65 m/s to 2 d.p. which is 28.3 mph to 1 d.p.

Haven't checked it through, think it's ok though, might be some typos 

10^2 = 20mu*d

Thus 100= 20 mu * 17.5

mu= 100/(20*17.5)= 100/350 =0.286 , which when rooted = 0.534 Very close mate. First one, perfect.

Obviously your value of mu would determine the answers to the rest of the question, but I got a value of v as 12.7 metres per second, so 12.7/0.447= 28.3

Well done.

[ipod05]

ugh! i hate math.. LOL..

math is my worst nightmare!!!

u get use to it, trust me

[Takashi]

10^2 = 20mu*d

Thus 100= 20 mu * 17.5

mu= 100/(20*17.5)= 100/350 =0.286 , which when rooted = 0.534 Very close mate. First one, perfect.

Obviously your value of mu would determine the answers to the rest of the question, but I got a value of v as 12.7 metres per second, so 12.7/0.447= 28.3

Well done.

Where did the 20 randomly come from?

[freefallz]

Wow this thread is still alive.


Go the power of MATH!!!!

Okay just to keep the thread going here's a question:
What do you call a polygon with infinite sides?

[jd1478jd]

doesn't exist does it?

What shape has infinite lines from its origin?

[shiro]

^ a circle

[freefallz]

zzZZzzz

zzZZ


This thread is missing some action.

[IniTiaL V.]

freefallz, watch channel 10

how many squares? the guy said 28 was the closest answer sofar, i think thers 42

[jd1478jd]

Where did the 20 randomly come from?

Sorry mate, actually can't remember? I'll try to redo it, and see if I do the same (Mistake??) again. 2

[jd1478jd]

You guys feel free to post any problems/debates here.