39
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:

If the velocity of a body is doubled its momentum ________________.

 

A) remains same   B) doubles  
C) becomes half   D) becomes 4 times  
 
Answer & Explanation Answer: B) doubles  

Explanation:
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2 198
Q:

A body of mass 8 kg is moving with a velocity of 4 m/s, find its momentum.

 

A) 2 B) 64
C) 32 D) 4
 
Answer & Explanation Answer: C) 32

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0 200
Q:

Ozone at the higher level of the atmosphere is a product of ______ acting on oxygen molecules.

 

 

A) IR radiation B) UV radiation
C) gamma rays D) x-rays
 
Answer & Explanation Answer: B) UV radiation

Explanation:
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1 866
Q:

'Torr' is a unit of _______.

 

A) force   B) energy  
C) power   D) pressure
 
Answer & Explanation Answer: D) pressure

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3 624
Q:

What is the velocity of sound in air?

 

A) 343 m/sec B) 110 m/sec
C) 220 m/sec D) 232 m/sec
 
Answer & Explanation Answer: A) 343 m/sec

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1 765
Q:

The power of a lens is —2.5 D. The type of lens and its focal length are respectively:

 

A) Convex, -0.40 m B) Concave, -0.40 m
C) Concave, 0.40 m D) Convex, 0.40 m
 
Answer & Explanation Answer: B) Concave, -0.40 m

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0 886
Q:

Which one of the following is the unit of force?

 

A) Pascal B) Watt
C) Joule D) Newton
 
Answer & Explanation Answer: D) Newton

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0 530
Q:

Which of the following are Mechanical waves?

 

A) X rays B) Radio waves
C) Microwaves D) Sound waves
 
Answer & Explanation Answer: D) Sound waves

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2 842