Physics Questions

Q:

On which day ' National Science Day ' is celebrated in India ?

A) February 23 B) February 25
C) February 26 D) February 28
 
Answer & Explanation Answer: D) February 28

Explanation:

National Science Day is celebrated in India on 28 February each year to mark the discovery of the Raman effect by Indian physicist Sir Chandrashekhara Venkata Raman on 28 February 1928.

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Q:

When white light passes through a glass prism we get a spectrum on the other side of the prism. In the emergent beam the ray which is deviated least is

A) the violet ray B) the red ray
C) the green ray D) the blue ray
 
Answer & Explanation Answer: B) the red ray

Explanation:

Red is deviated the least and violet the most

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14 6191
Q:

A tennis ball machine serves a ball vertically into the air from a height of 2 feet, with an initial speed of 110 feet per second. After how many seconds does the ball attain its maximum height?

A) 2.87 sec B) 3.44 sec
C) 4.65 sec D) 5.41 sec
 
Answer & Explanation Answer: B) 3.44 sec

Explanation:

It is launched vertically with an initial speed of 110 ft/sec.

It will reach maximum height when the speed drops to 0.

Vo=110 feet per second 

ho=2 feet 

So, h(t) = -16t^2 +110t +2 

Take the derivative: h'(t) = 110 -32t 

The maximum height will be at the inflection when the derivative crosses the x-axis, then h'(t)=0. 

So, set h'(t)=0 and solve for t: 

0 = 110 -32t 

-110 = -32t 

t=3.4375 

t=3.44 seconds.

 

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Q:

When a steel ball is placed on the surface of mercury, it does not sink because

A) of the surface tension of mercury B) mercury is a semisolid
C) of the high viscosity of mercury D) the density of mercury is greater than that of steel
 
Answer & Explanation Answer: D) the density of mercury is greater than that of steel

Explanation:

A solid sinks in a liquid if its density is greater than that of the liquid. if less, it floats

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8 6143
Q:

A stone floor feels cold to the bare feet but a carpet on the same floor feels warm. This is because 

A) the floor and carpet are at different temperatures B) the stone conveys the heat away from the feet more rapidly than the carpet
C) the carpet is a better conductor of heat than the stone D) the human body maintains a constant temperature
 
Answer & Explanation Answer: B) the stone conveys the heat away from the feet more rapidly than the carpet

Explanation:

Both the floor and the carpet have the same temperature as both are exposed to the same atmosphere. But the former conducts away the heat from the feet better than the carpet as the latter is a non-conductor. So the feet losing more heat, the floor appears cooler to the feet.

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6 6133
Q:

Water kept in an earthen pot is less cool on rainy days than in summer because during the rainy days 

A) the pores in the pot are closed B) rain water stops oozing out from the pores
C) the water that oozes out does not evaporate quickely because of the large percent age of moisture in the air D) surface of the pot becomes damp
 
Answer & Explanation Answer: C) the water that oozes out does not evaporate quickely because of the large percent age of moisture in the air

Explanation:

To evaporate the water that oozes out, heat is required. Part of this heat is taken from the water inside which therefore become cool. Therefore (C) is correct. Here evaporation is less, so cooling too is less.

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Q:

Hydrogen atom is excited from ground state to another state with principal quantum number equal to 4. Then the number of spectral lines in the emission spectra will be

A) 2 B) 6
C) 5 D) 3
 
Answer & Explanation Answer: B) 6

Explanation:

Number of spectral lines from a state n to ground state is

 

                   n(n-1)/2 = 6

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Q:

Low voltage cables are meant for use up to

A) 3.3 kV B) 1.1kV
C) 11 kV D) 0.5 kV
 
Answer & Explanation Answer: B) 1.1kV

Explanation:

Low Voltage Cables are used to supply power for use up to 1.1 kV.

low_voltage_cables_are_meant_for_use_up_to1553167280.jpg image

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