Question

Please help with this trig problem:

find velocity for:
a point on the edge of a flywheel of radius 2m, rotating 42 times per minute

Answer 1

This isn't really a trig problem, but it requires a loose understanding of radian measure and finding arc lengths.

Answer 2

velocity is distance ÷ time; the distance here is the arc length. Arc length is angle (in radians) × radius.
The 'per minute' from the rotational speed will come along for the ride.

Answer 3

I already did the math but i am not sure if the answer i got was correct.
The answer i got was about 8.8m per minute

Answer 4

8.8? That seems really slow for a 2m wheel at 42rpm. How did you get that?

Answer 5

The formula in my book that it said to use was v=rw
r=2
in order to get w i first have to:
42(2pi)=84pi
w= 84pi/60 reduce to 7pi/5
So then:
2(7pi/5)=2.8pi or about 8.8

Answer 6

Why 84π/60? Do you want the velocity in m/s?

Answer 7

i thought that was how you would get "per minute"

Answer 8

Only if you were give angular speed in 'per hour'

Answer 9

Your given rotational speed is in units of per-minute, so leave the units of time alone unless you want to convert it to something else.

Answer 10

If you want in m/s then yes it's about 8.79m/s at the edge.

Answer 11

so that's the answer?

Answer 12

If it doesn't specify what units to express the velocity, then I would keep it in per-minute units because those are the ones given. In that case, the speed at the edge is about 500m/min. The measure of the radius isn't given with much precision, so I don't feel comfortable giving a more precise answer than that.
If you want the velocity in m/s then divide by 60 to get the 9 or so m/s.

Answer 13

so then i don't have to divide 84pi by 60?