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# Daily Archives: June 19, 2011

## Effect on Time Period of a Simple Pendulum

“The bob of a simple pendulam is of iron.If a small magnet is placed just under the bob,then how the time period will be affected?”

Question Posted by Riya Mondal

The time period will decrease as the attraction of magnet increases the net downward pull (adding to g in the equation $T=2\pi \sqrt{\frac{l}{g}}$)

(It was a quick answer; Visitors are requested to respond)

## Negative Mass

“Can mass be a negative? if yes plz explain me…”

Negative mass is a hypothetical concept. In normal case mass is always positive as it is of one kind only.

Some argue that this (+ mass) is in our universe (?) and there is equal probability of having a negative mass somewhere else.

In Casimir Effect ( A quantum phenomena :: Find details at http://en.wikipedia.org/wiki/Casimir_effect) properties similar to the expectations from negative mass were reported. (i.e; then the force between two masses becomes repulsive)

The concept of negative mass and the consequences thereof are widely discussed in the theory of wormhole and related ideas.

The existence of negative mass will violate more than one conservation principles in its present form.

## Thermal Expansion Problem

A metre scale is calibrated at 0 degree celsius to give correct reading. Find the distance between 50 cm and 51 cm if the scale is used at 10 degree celsius. Coefficient of linear expansion of steel is 1.1×10-5

Answers given in two books are 1.00011cm and 0.99988 why this contradiction?

(The question is being posted at PhysicsForum.PlusTwoPhysics.com too so that visitors can readily reply with their answers and explanations)

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