Q-1: Weight of Body on False Balance Q-2: Maximizing Energy in Swimming

[shobhitdimple]

Q-1 : A bodu weighs 8 gm when placed in one pan and 18 when placed on a other pan of a false balance . If the beam is horizontal when both the pans are empty , the true weight of the body is

Q-2 : when one swims across a river max. energy is spent in second 1/3 of the distance why ?

 

[Redbelly98]

Welcome to PF.

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[tomcue]

Q-1: The true weight of the body can be calculated by using the principle of moments. Since the beam of the balance is horizontal when both pans are empty, it means that the moments on both sides are equal. Therefore, we can set up an equation using the moments on each side and solve for the unknown weight of the body.

Q-2: When swimming across a river, the maximum energy is spent in the second 1/3 of the distance because this is when the swimmer is facing the most resistance from the water. In the beginning, the swimmer is building up momentum and in the final 1/3 of the distance, the swimmer is slowing down due to fatigue. Therefore, the middle 1/3 of the distance requires the most effort and energy to overcome the resistance of the water. Additionally, this is when the swimmer is moving against the current of the river, which adds to the resistance and requires even more energy expenditure.