40
Q:

A boat loaded with rocks floats in the middle of a swimming pool. A man in the boat throws the rocks overboard. The level of water in the pool will

A) increase B) decrease
C) remains the same D) first decrease and then increase

Answer:   B) decrease



Explanation:

Let M and m grams be the mass of boat + rock in it. By law of floatation(M+m) grams of water will be displaced. This has a volume of (M+m)cc. That means the level of water in pool has risen up by (M+m)cc with the boat + rock when it is floating. If the rocks in the boat are thrown not into the pool but outside, the weight left is only M grams the weight of the boat. This will have displaced M cc of water only i.e less water than in the case of loaded boat. But if the rocks are put in the water in the pool and not outside, then the water in the pool will rise not only by M cc on account of empty boat but also by a volume of the stone put into it. This volume will be mdwhere m is the mass of rock and d density of rock.

Now md is  < m. Thus the total rise will be M+mdwhich is < M + m.

Subject: Physics
Exam Prep: AIEEE , CAT
Job Role: Analyst
Q:

Identify the unit of measuring intensity of sound.

 

A) Decibels B) Knots
C) Candela D) Ampere
 
Answer & Explanation Answer: A) Decibels

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Q:

Which instrument is used to measure blood pressure?

 

A) Sphygmomanometer B) Lactometer
C) Thermometer D) Glucometer
 
Answer & Explanation Answer: A) Sphygmomanometer

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Q:

The term ______ is prefixed to scientific terms to describe something that is constant.

 

A) Photo B) Iso
C) Mega D) Quasi
 
Answer & Explanation Answer: B) Iso

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0 117
Q:

1 horsepower = approximately _____ watts.

 

A) 746 B) 764
C) 647 D) 674
 
Answer & Explanation Answer: A) 746

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3 188
Q:

Which law of physics states that the force between the two electric charges reduces to a quarter of its former value when the distance between them is doubled?

 

A) Coulomb’s Law B) Stefan's Law
C) Pascal's Law D) Hooke's Law
 
Answer & Explanation Answer: A) Coulomb’s Law

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0 285
Q:

What is the unit of measure of a magnetic field?

A) Cobalt B) Ohm
C) Tesla D) Ampere
 
Answer & Explanation Answer: C) Tesla

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3 234
Q:

_______ expansion makes the Eiffel Tower taller during summers.

 

A) Thermal   B) Chemical  
C) Gravitational   D) Gradient  
 
Answer & Explanation Answer: A) Thermal  

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3 1500
Q:

Georg Simon Ohm in whose honour we have the famous Ohm’s Law, hailed from which country?

 

A) Russia B) Spain
C) Poland D) Germany
 
Answer & Explanation Answer: D) Germany

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