Question

# Position a pole across the back of a chair (serving as a fulcrum) and hang a...

Position a pole across the back of a chair (serving as a fulcrum) and hang a two ­pound weight on one end of the pole. Position a five ­pound weight on the other side of the pole such that the weights are balanced. Measure and record the distances of the two weights from the fulcrum and write an explanation of your results.

Distance of 5­lb weight from fulcrum: ?

Distance of 2­lb weight from fulcrum: ?

Explanation:

The fulcrum is acting as the pivot point of rotation, and both the weights of 5lb and 2lb are applying equal torque and opposite in direction of each .

Suppose the length of the pole is 1m. Now let us take the distance of weight 2lb from fulcrum be 'x' so the distance of weight from fulcrum will be '1-x' .

Torque applied by weight 2lb = 2gx

torque applied by weight 5lb = 5g(1-x) = 5g - 5gx

Since both weights balance each other that means torque applied bu them is equal to each other.

So 2gx = 5g - 5gx

=> 2x = 5 - 5x

=> x = 5/7

So the distance of block of weight 2lb from fulcrum is 5/7 = 0.714m

And distance of block of weight 5lb from fulcrum is 1 - 5/7 = 2/7 = 0.286m

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