Rotation of Rigid Bodies- mastering physics 9.72

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Homework Help Overview

The discussion revolves around a problem involving the rotation of rigid bodies, specifically focusing on a table saw's motor speed, the tangential speed of a saw blade, and the radial acceleration of points on the blade's edge.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the conversion of motor speed from revolutions per minute to radians per second and the relationship between linear speed and angular velocity. Questions arise regarding the calculation of the radius of the saw blade and the rotational speed of the second shaft connected by a V-belt.

Discussion Status

Some participants have provided guidance on using the diameter of the saw blade to find its radius and have discussed the implications of the pulley system on the rotational speeds. Multiple interpretations of the relationship between the shafts are being explored.

Contextual Notes

The problem presents constraints such as the lack of explicit radius information for the second pulley and the need to consider the different rotational speeds of the connected shafts.

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The motor of a table saw is rotating at 3450 rev/min. A pulley attached to the motor shaft drives a second pulley of half the diameter by means of a V-belt. A circular saw blade of diameter 0.208 m is mounted on the same rotating shaft as the second pulley.
PART A: The operator is careless and the blade catches and throws back a small piece of wood. This piece of wood moves with linear speed equal to the tangential speed of the rim of the blade. What is this speed?
PART B:Calculate the radial acceleration of points on the outer edge of the blade to see why sawdust doesn't stick to its teeth.

I converted 3450 rpm to 361.283 rads/s. I know that v=rw, but how do I calculate this without the radius being given?
 
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Well they gave you the diameter of the saw blade, so you can divide that by two to get its radius. There's an additional step though, you need to take account of the fact that the shaft which is driving the blade is rotating at a different rate than the shaft which is connected to the motor.
 
Is the second shaft rotating twice as fast since its on a belt half the diameter of the first?
 
Got It. Thanks.
 

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