Solving Bacterial Motor Angular Speed and Time for One Revolution

[neoncrazy101]

Homework Statement

Some bacteria are propelled by motors that spin hair-like flagella. A typical bacterial motor turning at a constant angular velocity has a radius of 1.8x10-8m, and a tangential speed at the rim of 1.8x10-5 m/s. (a) What is the angular speed (the magnitude of the angular velocity) of this bacterial motor? (b) How long does it take the motor to make one revolution?

Homework Equations

Vt= rw
rad/s / 2pi = rev/s

The Attempt at a Solution

I got part A which is 1000rad/s. but Part B I can't get. If its supposed to be 1000/2pi = 159.15 then something is wrong. I know I'm missing something cause the answer my homework program is giving me is .0063s. So what equation should I be using?

 

[SteamKing]

In part b, you are supposed to calculate how long it takes to make one revolution. What is the formula for calculating the period?

 

[S_Happens]

If you write the units of your answer for B, you will see that it is rev/s, not s/rev which is what the question is asking for. It should be pretty easy to convert that one.

 

[neoncrazy101]

In part b, you are supposed to calculate how long it takes to make one revolution. What is the formula for calculating the period?

T=(2pi(r))/V ?

 

[SteamKing]

If a shaft rotates at 10 revolutions per second, how long does each revolution take?

 

[neoncrazy101]

.1 seconds.

OH! I think I got it thanks.

So I take the 1000/2pi to get the 159.xxx and then do 1/159 = .0062893 and round to get .0063. thanks!