(Eng. mechanics) The minimum radius, r, required of a cylindrical rod, such as that used o...

(Eng. mechanics) The minimum radius, r, required of a cylindrical rod, such as that used on a bicycle pedal (see Figure), to provide enough support for the pressure exerted by the rider’s foot, yet not exceed the stress placed on the crank arm’s sprocket attachment, is determined by this formula:

r is the radius of the cylindrical rod in inches.

d is the length of the crank arm in inches.

P is the weight placed on the pedal in lbs.

S is the stress in lbs/in2. 

Figure: Determining the radius of a bicycle’s crank arm

a. Determine the value of r for a crank arm that’s 7 inches long, must accommodate a maximum weight of 300 lbs, and be able to sustain a stress of 10,000 lbs/in2.

---

b. If you were asked to write a computer program to determine the radius of the cylindrical rod for a bicycle’s crank arm, what inputs, outputs, and algorithm would your program require?