EXPERIMENT

OBJECTIVE:

To verify the law of polygon of forces with the help of universal force table apparatus.

APPARATUS:

Universal Forces table with five pulleys, rings with five string weight, slotted weight, plain paper and geometry box.

THEORY:

Polygon law of forces states that if a number of concurrent forces are acting simultaneously on a body, are represented in magnitude and direction by the sides of a polygon, taken in order, then the resultant is represented in magnitude and direction by the closing side of the polygon, taken in opposite order.

PROCEDURE:

• Before starting the experiment make the graduated table horizontal with the help of leveling screw.

• Clamp the pulley to the graduated disc of the force table.

• Tie one and of thread to the circumference of small rings and place it around the central axis of the apparatus.

• Attach other end of the string to the weight hangs which will carry small slotted weight.

• Pass one string over each pulley.

• Place slotted weight on the weight hanger in such a manner that ring is placed around the center.

• Note down the angle between different threads and corresponding weights.

• Draw a space diagram of the force acting a part such that the time of action of each force corresponding to the angles of forces between them.

• Chose a suitable scale and make mark a point on a paper and draw the vector diagram of force system acting at a point by drawing parallel line of each force proportional to the chosen scale.

Procedure to draw vector diagram:

• Draw a line OA parallel and equal to W1 assuming a suitable scale.

• Draw a line AB parallel and equal to W2 from point A assuming the same scale.

• Similarly draw BC and CD parallel and equal to the force W3 and W4.

• Join OD i.e. the closing side by dotted line, which represents the resultant of polygon (graphically).

• Measure the line OD and compare it with W5 by using the same scale.

• Find the error by using the formula given in the observation table. Error should be positive.

OBSERVATION TABLE:

PRECAUTIONS:

• Ring should not touch the control axle of the disc and should be at the center of the table.

• Graduated disc should be made kept perfectly horizontal.

• Positions of the strings should be at the center of the table.

• Pulley should be frictionless.

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