Writing and Using a Quadratic Model
BLOCK AND TACKLE
An object lifted with a rope or wire should not weigh more than the safe working load for the rope or wire. The safe working load S (in pounds) for a natural fiber rope is a function of C, the circumference of the rope in inches.
Safe working load model:
You are setting up a block and tackle to lift a 1350-pound safe. What size natural fiber rope do you need to have a safe working load?
SOLUTION
Use the model to find a safe rope size. Substitute 1350 for S.
Write model.
Substitute.
Subtract 1350 from each side.
Factor out common factor.
Factor.
or Use zero-product property.
Set first factor equal to 0.olve for C.
Solve for C.
Set second factor equal to 0.
Solve for C.
The negative solution makes no sense. You need a rope with a circumference of at least 3 inches.