Solve Rotation Problem: Wheel w/ 8 Spokes & 30cm Radius

  • Thread starter ChazyChazLive
  • Start date
  • Tags Tags
    Rotation
2 replies · 8K views · last reply
ChazyChazLive
Messages
18
Reaction score
0

Homework Statement


The wheel in Fig. 10-29 has eight equally spaced spokes and a radius of 30 cm. It is mounted on a fixed axle and is spinning at 3.6 rev/s. You want to shoot a 26-cm-long arrow parallel to this axle and through the wheel without hitting any of the spokes. Assume that the arrow and the spokes are very thin. What minimum speed must the arrow have?
Diagram of a wheel with eight equally spaced spokes on a central hub, shown in perspective. A red curved arrow indicates the direction of rotation, and gray arrows show a thin arrow passing parallel to the axle through the wheel.


Homework Equations




The Attempt at a Solution


Okay so first i wrote down my givens.
I found the angle between the spokes to be 45 or pi/4 radians.

I did the 3.6rev/s time 2pi rad/rev which equals 7.2pi radians/s. That would be the angular velocity.
I did pi/4 radians divided by 7.2 pi radians/s which equals 0.03472s for time.
Now, I'm kinda stuck.
Any help would be grateful. Thankyou!
 

Discussion

You should see that the arrow only has 0.034s to travel 26 cm...
 
heh.. i feel kinda stupid now...

thank you for the help agh.. it was so obvious i didn't see it >.<