wheel and axle

round and round it goes

A wheel and axle is a simple machine that consists of two connected rings or cylinders, one inside the other. Both rings or cylinders turn in the same direction around a single center point. The inner ring or cylinder is called the axle, and the outer one is called the wheel. Besides the Ferris wheel, the doorknob in the Figure 1.1 is another example of a wheel and axle. In a wheel and axle, force may be applied either to the wheel or to the axle. This force is called the input force. A wheel and axle does not change the direction of the input force. However, the force put out by the machine, called the output force, is either greater than the input force or else applied over a greater distance. A: In a Ferris wheel, the force is applied to the axle by the Ferris wheels motor. In a doorknob, the force is applied to the wheel by a persons hand.

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mechanical advantage of a wheel and axle

The mechanical advantage of a machine is the factor by which the machine changes the input force. It equals the ratio of the output force to the input force. A wheel and axle may either increase or decrease the input force, depending on whether the input force is applied to the axle or the wheel. When the input force is applied to the axle, as it is with a Ferris wheel, the wheel turns with less force. Because the output force is less than the input force, the mechanical advantage is less than 1. However, the wheel turns over a greater distance, so it turns faster than the axle. The speed of the wheel is one reason that the Ferris wheel ride is so exciting. When the input force is applied to the wheel, as it is with a doorknob, the axle turns over a shorter distance but with greater force, so the mechanical advantage is greater than 1. This allows you to turn the doorknob with relatively little effort, while the axle of the doorknob applies enough force to slide the bar into or out of the doorframe.

instructional diagrams

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questions

examples of wheels and axles include

a) ferris wheels.

b) doorknobs.

c) steering wheels.

-->  d) all of the above

the input force may be applied either to the wheel or the axle of a wheel and axle.

-->  a. true

b. false

a wheel and axle changes the direction of the input force.

a. true

-->  b. false

which statement about a ferris wheel is true?

-->  a) the input force is applied to the axle.

b) the input force is less than the output force.

c) the output distance is shorter than the input distance.

d) none of the above

which statement about a doorknob is false?

a) the input force is applied to the wheel.

-->  b) the input force is greater than the output force.

c) the mechanical advantage is greater than 1.

d) the input distance is longer than the output distance.

a wheel and axle may either increase or decrease the input force.

-->  a. true

b. false

diagram questions

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