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WHEEL
AND AXLE
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| It is a simple machine and is used to lift heavy loads. It has a wheel of larger radius (R) and an axle of smaller radius (r) fixed on the same shaft. Wheel and axle are free to rotate about its shaft. | |||
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MECHANICAL
ADVANTAGE OF WHEEL AND AXLE
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| The effort is applied to the rim of the wheel and the load is raised by a rope wound around the axle. | |||
| In one rotation wheel covers a distance of 2pR | |||
| In one rotation load is raised by a distance of 2pr | |||
| If we neglect force of friction, | |||
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Output
= input
W x 2pr = P x 2pR W/P = 2pR/2pr W/P = R/r |
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| Since [W/P = M.A.] | |||
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M.A.
= R/r
OR M.A. = radius of wheel / radius of axle |
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This
expression indicates that in order to increase the mechanical advantage
 Radius
of :wheel must have a large value. Radius
of axle must be smaller than that of wheel. |
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| For latest information , free computer courses and high impact notes visit : www.citycollegiate.com | |||
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WEDGE
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| Wedge is also a type of simple machines. It is used in levers as a fulcrum. It is also used for splitting the wood in to small pieces. It is used as an Ax. | |||
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CONSTRUCTION
OF
WEDGE |
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| A wedge is made of two inclined planes joined together. The effort ‘P’ is applied on the top of the wedge placed over a wood log. The wedge enters the wood and splits it. The reaction forces R1 & R2 are acting perpendicular on the inclined planes of the wedge. These forces and resultant frictional forces are responsible for keeping the wedge inside the wood firmly. | |||
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MECHANICAL
ADVANTAGE OF WEDGE
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| Let us consider that the wedge is in equilibrium under the action of forces three forces R1, P and R2 and neglecting frictional forces. According to figure below the forces P, R1 and R2 are represented by the sides of D XYZ such that effort P the reaction R1 and R2 are represented by XY, YZ, ZX which are the sides of ,D XYZ respectively. | |||
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Mechanical
advantage(M.A). = load/effort
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| For equal sides of wedge i.e. = R1 = R2 = R | |||
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M.A.
= R/P
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M.A
= ZX/XY
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| Triangle ABC and triangle XYZ are similar, therefore, | |||
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ZX=AC and XY=BC
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M.A.
= AC/BC
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Mechanical
advantage = length of inclined surface of wedge/thickness of wedge
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| From above expression it is clear that if the thickness of the wedge is decreased the mechanical advantage of the wedge will increase & if the wedge is more sharper , then the mechanical advantage will increase. | |||
| For latest information , free computer courses and high impact notes visit : www.citycollegiate.com | |||