Imagine that you are a mechanical engineer, designing a motor for a sports car p
ID: 2091782 • Letter: I
Question
Imagine that you are a mechanical engineer, designing a motor for a sports car production line. You have been asked to design a safety cut-off - something that will switch the motor off if for any reason it starts to rotate faster than 114.355 rotations per minute.
You have come up with the design below: (I have tried to insert this again)
The engine causes the grey rod (of radius 0.482 m) to rotate around the axis of rotation. Sticking out from this rod are two slider poles. On each slider is threaded a weight of mass 0.857 kg, which can slide frictionlessly along the sliders. The weights are attached to the rod with springs of spring constant 414.387 N m-2 and unstretched length 0.173 m.
As the rod rotates, centrifugal force will push the weights further out along the sliders. You plan to place a sensor a distance r from the the axis of rotation, and if the weights move this far out, the slider will switch off the engine.
Explanation / Answer
kr=mwr^2
414.387 ( r -0.173 -.482)=0.857*(114.355*2*pi/60)*r^2
solving, r=39.71m