Physics buffs, I NEED YOU!

[WorldIndustries]

I need help with my physics assignment... I was sick for the past few weeks, and I missed a lot of classes. I have no idea what's going on. Even though I have notes, nobody explained them to me. So I'm gonna be asking a few questions over the next couple hours, hopefully someone can help me with this stuff...

First, I'm having a problem converting RPM to m/s... The RPM is 45, radius is 8.9 meters, and I keep calculating 25.16 m/s... Is this right?

 

[WorldIndustries]

Nevermind, got it, it's 0.75 m/s, I it was 8.9 centimetres, I read it wrong... I will still be asking more questions, soon!

 

[HAVOC]

May I suggest you visit a community that specializes in physics?

http://www.physicsforums.com/

Just a thought?

 

[Meithan]

You're in luck, I'm in the last semester of a Physics major.
EDIT: Ok, correcting the radius to 8.9 centimeters:

You want to convert RPM to tangential speed. Easy:

1) 45 RPM means there are 45 rotations per minute, so dividing by 60 we get 45/60 = 0.75 rotations per second.

2) Now, the radius of rotation is 8.9 centimeters, so the "length of one rotation" is just the 2 * PI * R (perimeter of a circle, the usual formula). So the length of the rotation is: 2 * PI * (8.9cm) = 55.9cm (rounded to 1 decimal). In meters, this is 0.559m or 0.56m if we round.

3) Ok, so there are 0.75 rotations per second, and each rotation goes through 0.56m. Remember speed = distance / time, but in this case we can see it as speed = length of one rotation * rotations per second. We thus get speed = 0.56m * 0.75 RPS = 0.42m/s.

I still get a slightly different result.

 

[HAVOC]

You're in luck, I'm in the last semester of a Physics major.

Physics Major. God you must either love it or just really get it.
Good for you man.

 

[superdave1984]

OMG, there are physics buffs??? ARMAGEDDON!

 

[WorldIndustries]

Ahh... What about this one... The end of a race track is in the shape of a half-circle and has a width of 500m. The curve is designed with an incline to safely allow cars to traverse the curve at top speeds of 120 km/h. At the outer edge of the curve, what is the height of the incline?

So far, I've converted the velocity to 33.3 m/s [from 120 km/h], and I have the radius of 500 (I may be wrong, perhaps it's 250?)

And I know it has to do with the formula:


Radius = velocity² / (-9.8) TanΘ

 

[bum]

OMG, there are physics buffs??? ARMAGEDDON!

I didn't get physics much. I don't get anything that mixes something else with math.

 

[ncjimn]

I did this stuff last semester. Basically I don't remember anything, this semester we are doing electricity and magnetism. I know I'm not helping; I would, but I had to sell my book...so no book, I think my notes are gone too

 

[dawizhacker]

I'm like a MATH GOD, but when it comes to physics, I'm like a maroon. Thank god there are people like you Meithan. Thank YOU.