Question

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1. When a piece of wood is suspended from the hook of a spring balance , it reads 70 gf . The wood is now lowered into water . What reading do you expect on the scale of spring balance?
2. A balloon filled with helium gas floats in a big closed jar which is connected to an evacuating pump. What will be your observation, if air from jar is pumped out? Explain your answer..
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Answer 1

APPEARS IN

When a Piece of Wood is Suspended from the Hook of a Spring Balance, It Reads 70 Gf. the Wood is Now Lowered into Water. What Reading Do You Expect on the Scale of Spring Balance? Concept: Floatation - Principle of Floatation

Answer 2

Answer:

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Explanation:

1.When the wood is lowered into water, the wood will float in water.

1.When the wood is lowered into water, the wood will float in water. So, its apparent weight = weight of the block in air − upthrust

1.When the wood is lowered into water, the wood will float in water. So, its apparent weight = weight of the block in air − upthrustNow, the piece of wood is floating implies that the upthrust is equal to the weight of the block in air.

1.When the wood is lowered into water, the wood will float in water. So, its apparent weight = weight of the block in air − upthrustNow, the piece of wood is floating implies that the upthrust is equal to the weight of the block in air.Thus, the apparent weight of a floating body is zero. The spring balance will read zero

2.Explanation: As air is pumped out from jar, the density of air in jar decreases, so the upthrust on balloon decreases. As weight of balloon exceeds upthrust on it, it sinks.