## help!!!!!!

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steve
Posts: 2
Joined: Fri Mar 09, 2007 4:51 pm

### help!!!!!!

I need help with the following question becuase I don't know *** about physics, I'm a biologist but I made a bet with this hot girl and if I'm right I win something better than a cup of coffee. Question is= if your towing a trailer at 60mph and you have a 20inch tire on your car and a 12inch tire on your trailer,
Which tire is going faster and why? I said they are both the same.

artist
Posts: 68
Joined: Mon Nov 27, 2006 3:20 am
Depends on what you mean by "going faster." The smaller wheel would turn more times per second, but points on the surface of each tire would have the same speed.

Posts: 3
Joined: Fri Mar 09, 2007 6:12 am
Well. it depends on the radius of the tire.

steve
Posts: 2
Joined: Fri Mar 09, 2007 4:51 pm

### help2!!!!!!!

let me put it this way, If you look at a tire on a rim that is rotating at 60mph
both the rubber tire and the rim are revolving at the same speed right? even though the rim has to make more revolutions to cover the same distance as the tire. or if you took a 9" paper plate put an axis directly in the center, mark an "a" one inch out from the center and a "b" 7inches out then spun the plate.
Would "a" and "b" move at the same speed even though "b" is covering more distance durring one revolution

kutztown
Posts: 4
Joined: Mon Mar 05, 2007 6:01 pm
Same Angular velocity but diff Linear velocity

artist
Posts: 68
Joined: Mon Nov 27, 2006 3:20 am
Definitely not the same angular velocity. Consider a car with two wheels that travels one mile per hour. One of its tires has a one mile circumference. The other has a one foot circumference. The large wheel rotates at one turn per hour (2pi/hr) and the small wheel rotates 5280 times per hour.

However, consider a point on the surface of each wheel. Relative to the car, a point on the surface of the big wheel moves through 1 mile of circumference in an hour. A point on the small wheel rotates moves through 5280 turns * 1 foot per turn = 5280 feet = 1 mile in an hour. So relative to the car, they both have a linear speeds (at the outer edges of the tires) of one mile per hour.

kutztown
Posts: 4
Joined: Mon Mar 05, 2007 6:01 pm
@ Artist

" Same Angular velocity but diff Linear velocity" was in response to Steve's second post about the paper plate. In that case is " Same Angular velocity but diff Linear velocity" correct?

artist
Posts: 68
Joined: Mon Nov 27, 2006 3:20 am
Oh, yes. Sorry.

@steve: I hope you understand that the two situations you have described are not the same.