Question

Difficulty: MediumWheel and Axle

A manual meat grinder is operated by turning a crank handle. The crank arm has a length of 8.0 inches8.0 \text{ inches} (acting as the radius of the wheel). The internal grinding shaft, which acts as the axle, has a diameter of 1.6 inches1.6 \text{ inches}. If a user applies a steady perpendicular force of 15 pounds15 \text{ pounds} to the crank handle, what is the resulting theoretical output force (in pounds) exerted at the outer surface of the grinding shaft? Assume 100%100\% efficiency.

Answer: 150 pounds

Answer

150
The machine multiplies the input force based on the ratio of the crank arm radius to the grinding shaft radius. Converting the 1.6 inch1.6 \text{ inch} axle diameter to a 0.8 inch0.8 \text{ inch} radius gives an Ideal Mechanical Advantage (IMA) of 1010 (8.0÷0.88.0 \div 0.8). Multiplying the 15 pound15 \text{ pound} input force by this IMA results in a 150 pound150 \text{ pound} theoretical output force.

Step-by-Step Solution

1
Determine the radius of the axle.
Axle radius = 0.8 inches0.8 \text{ inches}
The Ideal Mechanical Advantage formula requires comparing equivalent radial measurements. Since the wheel dimension is given as a radius, converting the axle's diameter to a radius ensures units are consistent.
2
Calculate the Ideal Mechanical Advantage (IMA).
IMA=10IMA = 10
Dividing the wheel radius (8.0 inches8.0 \text{ inches}) by the axle radius (0.8 inches0.8 \text{ inches}) determines the mechanical advantage multiplier of the machine.
3
Calculate the theoretical output force.
Output Force = 150 pounds150 \text{ pounds}
Multiplying the input force (15 pounds15 \text{ pounds}) by the mechanical advantage (1010) yields the final output force exerted at the axle surface.

Key Concept

The Ideal Mechanical Advantage (IMA) of a wheel and axle is the ratio of the wheel's radius to the axle's radius. The resulting output force is equal to the input force multiplied by this mechanical advantage.
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