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# Inclined Plane, Hydraulic Press, Screw

An inclined plane is a sloping surface used for pulling or pushing a load up, rather than lifting them vertically.

Velocity Ratio =Distance moved by EffortDistance moved by Load=xh

Velocity Ratio =1sinθ

# Hydraulic Press

Definition of Hydraulic Press

Hydraulic press is a device used to produce a very large force to compress or lift up a heavy load. It is used in the printing press where a large force presses the type with ink on it against the paper. Pressure is transmitted equally to all parts of a liquid at the same level.

## Animation: Observe and explain what is going on using the comment box:

If A1 is the area of small piston and A2 area of the large piston, pressure(P) is transmitted equally at the same level, then

P=EA1,E=P×A1P=LA2,L=P×A2

Therefore a small effort lifts a large load.

M.A=LE=A2A1=R2r2

If x and y are the distances moved by E and L respectively,  A1x = A2y

xy=A2A1=R2r2=V.R

Example 2:

An inclined plane of angle 150 is used to raise a load of 4500N through a height of 2m. If the plane is 75% efficient, calculate (i) Velocity ratio of the plane (ii) Work done on the load

Solution:

M.A=LE=A2A1=R2r2LE=A2A1L=A2×EA1=200×4010=800N

EVALUATION

A man pulls up a box of mass 70kg using an inclined plane of effective length 5m onto a platform      2.5m high at uniform speed. If the frictional force between the box and the plane is 100N, draw the diagram of all the forces acting on the box when in motion and calculate the

(i) Minimum effort applied in pulling up the box

(ii) Velocity ratio of the plane

(iii) Mechanical advantage of the plane

(iv) Efficiency of the plane

(v) Energy lost in the system

(vi) Work output of the man

(vii) power developed by the man given that the time taken to raise the box onto the platform is 50s. ( g = 10m/s2)

# Screw

Definition of Screw

A screw is mechanical fastening device consisting essentially of an inclined plane wound spirally around a cylinder or a cone. The ridges formed by the winding planes are called threads, and depending on the intended use, the threads may be square, triangular, or rounded in cross section.