Everything about Inclined Plane totally explained
» This article deals with the physical structure. For related terms see, canal inclined plane, cable railway, funicular, or fixed-wing aircraft (airplane). The
inclined plane is one of the original six
simple machines; as the name suggests, it's a flat surface whose endpoints are at different heights. By moving an object up an inclined plane rather than completely vertically, the amount of force required is reduced, at the expense of increasing the distance the object must travel. The
mechanical advantage of an inclined plane is the ratio of the length of the sloped surface to the height it spans; this may also be expressed as 1 divided by the
sine of the angle between the plane and the horizontal. Note that due to the
conservation of energy, the same amount of
mechanical energy is required to lift a given object by a given distance, except for losses from
friction, but the inclined plane allows the same work to be done with a smaller force exerted over a greater distance.
Ramps, Chutes and Slides
Many devices based on the principle of the inclined plane allow expending less force to achieve a task.
Ramps enable accessing heights that would be too difficult to scale vertically. Ramps allow heavy vehicles to ascend to, and descend safely from, a high-level bridge. Portable ramps allow easy loading and unloading of high-decked
trucks.
Siege ramps gave ancient armies the ability to walk up bringing heavy equipment to the tops of high walls.
Chutes and
Slides allow fragile objects, including
humans, to be safely lowered from a vertical rise by countering
gravitational force with the
normal force provided by a stiff surface at an angle to the gravitational
vector. Airplane rescue slides allow people to quickly reach the ground safely, without the danger of jumping from a height. The addition of the normal force and gravity vectors causes the sliding object to move parallel to surface of the slide, so a slide can be used to move objects through a distribution system from one area to another.
Hoppers and
funnels are formed by planes shaped into an inverted
pyramid or
cone shape to concentrate granular or fluid material at the apex.
Eliminating
friction from a slide increases the maximum speed at which an object can move down the slide, while the acceleration of the moving object can be controlled to any degree by varying the angle of the slide. Because of this, slides are one of the most common and popular forms of entertainment. A well-pollished slide can allow a human to move at a high speed with no effort, even experience near
free-fall acceleration, yet arrive on the ground safely because the angle of slide can be varied along its length to end up parallel to the ground, so the forward motion of the slider can be slowly arrested by friction. The metal slide is a popular piece of playground equipment, and towering
water slides employ liquid lubrication to reduce friction even further. Wheeled cars of
rollercoasters roll down inclined tracks to achieve high speeds. In the sports of
Luge,
bobsled,
sledding, and
skiing, participants accelerate to extremely high speeds utilizing only the inclined plane, whether a mountain slope provided by nature, or a chute lined with near-frictionless ice.
Blades, Wedges, and Foils
The
blade is a compound inclined plane, consisting of two inclined planes placed so that the planes meet at one edge. The edge where the two planes meet is pushed into a solid or fluid substance and overcomes the resistance of materials to separate by transferring the force exerted against the material into to opposing forces normal to the faces of the blade. First known to be used by humans in the
knife to separate animal tissue, the blade allowed humans to separate meat, fibers, and other plant and animal materials, with much less force than it would take to tear them by simply pulling them apart. Blades can separate solid material, as with
plows that separate soil particles,
scissors and
shears to cut flexible materials,
axes to separate wood fibers, and
chisels and
planes to remove precise portions of wood.
Wedges,
saws and
chisels can separate thick and hard materials, such as wood, including solid stone and hard metals, with much less force, less waste of material, and more precision, than
crushing. Saws have many chisel-like "teeth" along their cutting surface to transfer linear or circular motion to counteract the normal force of the surface to be cut.
Crushing, the overcoming of material bonds by transferring
momentum to a material through the
normal force of another, harder, object was the only way to
cut through a hard material before saws, and the materials to make them, were developed.
Drills produce circular holes in solids by rotating a chisel around its center, with the edge is sharpened at opposing angles on either side of the rotation axis, so as to cut in the direction of rotation.
Twist drills provide one or more
heliacally twisted chisels formed out of grooves cut along the side of the bit, to help evacuate cuttings from the drill hole, by using the same inclined plane principle as the
archimedean screw. The water screw, though most likely preexisting
Archimedes, has been used since ancient times to pump water, and is now also used to move granulated and ground materials, such as wheat, coal, and meat. Screws also join pieces of wood or metal together, by using a helical plane, usually formed by cutting a helical groove into a rod, to allow the rod force itself into the material when it's rotated.
The ancient
water wheel uses inclined planes mounted around a rotating wheel to transform the momentum of moving water into a
torque that can turn a shaft and do work.
Sails extract the momentum of moving air to drive a vehicle, and
windmills extend the principle to move a balanced set of sails around a shaft to perform work. Although known for thousands of years, these devices for extracting work from a moving fluid were always limited in efficiency by the
drag-inducing
vortices caused when a fluid is separated.
Foils are specialized blades, shaped to allow the most efficient movement of fluid over their surfaces, to minimize the
turbulence caused by these vortices. Rotating vortices dissipate the momentum of the fluid as heat, reducing the amount of energy available to do useful work.
Foils have many different designs, depending on the
viscosity,
velocity, and
pressure of the fluid that'll operate in, and their intended purpose.
Aircraft wings and
helicopter rotors counteract gravity by redirecting momentum generated from lateral movement, as with fixed-wing aircraft, or from rotating airfoils around a shaft, as with helicopters, so that separated air flows over the top of the foil faster than it flows over the bottom. This difference in velocity causes the pressure to increase on the bottom, generating a lifting force, through what is known as
Bernoulli's Principle. The same principle in reverse allows an automotive
spoiler to keep a car firmly in contact with the road.
Airplane and marine
propellers use the same principle to drive vehicles though a fluid along the direction of the torque applied to the propeller shaft. Nautical propellers are often called screws. Rotating
impeller blades increase the pressure difference between the inlet and outlet of a
pump to force fluids through pipes.
Turbines capture momentum from fast-moving fluid at high efficiency to a torque vector along the direction of the turbine's axis of rotation, while
compressors use rotational motion to increase the pressure in a fast-moving fluid.
Rotary fans move air, and can harness the reaction force of the moving air to drive a vehicle.
Calculation of forces acting on an object on an inclined plane
To calculate the forces on an object placed on an inclined plane, consider the three forces acting on it. Air resistance may be neglected for most calculations, except at high speeds.
- The normal force (N) exerted by the plane onto the body,
- the force due to gravity (mg - acting vertically downwards) and
- the frictional force (f) acting parallel to the plane.
We can decompose the gravitational force into two vectors, one perpendicular to the plane and one parallel to the plane. Since there's no movement perpendicular to the plane, the component of the gravitational force in this direction (
mgcos
θ) must be equal and opposite to normal force exerted by the plane,
N. If the remaining compnent of the gravitational force parallel to the surface (
mgsin
θ) is greater than the
static frictional force
fs - then the body will slide down the inclined plane with acceleration (
gsin
θ - f
k/m) - where f
k is the
kinetic friction force - otherwise it'll remain stationary.
When the slope angle (
θ) is zero, sinθ is also zero so the body doesn't move.
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