The edge of the wheel moves around more quickly, but with less force than the centre of the wheel. The middle of the wheel moves around more slowly but with more turning force than the outside of the wheel. Wheels on cars and lorries are attached to a pole called an axle, which passes through the centre of the wheel.
Ocean Acidification. Rising Sea Level. Wheel and axle. March 28, Simple machines [Online]. Contact us About us Privacy policy Terms of use. However, run-flats may require a specialized type of wheel. The least-expensive and most basic wheel is made of steel. Aluminum-alloy wheels come in various designs, and other than a small cover over the centre hub hole, seldom have anything added to them.
The wheel nuts are visible on many designs, and many drivers use locking ones to avoid someone stealing the wheels. While a deep-enough pothole can ruin just about anything, steel wheels are stronger than alloy wheels, which are easier to damage on rough roads or by brushing a curb.
Lighter alloy wheels are readily available in sizes up to 22 inches — and for ultimate customizers, right up to 30 inches or more.
Alloy wheels are also pricier, and to protect their investments from road salt, many people switch to plain steel wheels for their winter tires. The smaller steel wheel is fitted to a tire with a taller sidewall than the on the alloy wheel, so the outside diameters of both tire-and-wheel combinations are the same. This is important so that components calibrated to that diameter size function properly, such as the speedometer. There are a few other materials used for wheels, including lightweight forged aluminum and carbon fibre, but they can be very expensive.
Michelin currently sells one, the Tweel, for golf carts, and is working on one for cars. Also under development are in-wheel motors. Early wheels were likely made from stone or flat boards joined together into the form of a disk. To understand how wheels and levers work, we need to understand the concept of moment of a force. The moment of a force about a point is the magnitude of the force multiplied by the perpendicular distance from the point to the line of the force.
It all boils down to reducing friction. So imagine if you have a heavy weight resting on the ground. Newton's 3rd Law states that "For every action, there is an equal and opposite reaction". So when you try to push the load, the force transmits through the load to the surface it rests on. This is the action. The corresponding reaction is the force of friction acting backwards and is dependent on both the nature of the surfaces in contact and the weight of the load.
This is known as static friction or stiction and applies to dry surfaces in contact. Initially the reaction matches the action in magnitude and the load doesn't move, but eventually if you push hard enough, the friction force reaches a limit and doesn't increase further. If you push harder, you exceed the limiting friction force and the load starts to slide. Wheels eliminate this friction force by using leverage and an axle.
They still need friction so that they can "push back" on the ground on which they roll, otherwise slippage occurs. This force however doesn't oppose motion or make it more difficult for the wheel to roll. This analysis applies to the example above where the wheel is subject to a force or effort F at the axle. Two new equal but opposite forces are introduced where the wheel meets the surface. This technique of adding fictitious forces which cancel each other out is useful for solving problems.
When two forces act in opposite directions, the result is known as a couple and its magnitude is called the torque. In the diagram, the added forces result in a couple plus an active force where the wheel meets the surface.
The magnitude of this couple is the force multiplied by the radius of the wheel.
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