Tag: physics

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Questions Related to physics

Multiple choice archimedes' principle fluid pressure properties of matter physics

A vessel completely filled with water is weighed. This vessel will weigh ________ after a wooden block is gently moved into the water until it stays in equilibrium while any displaced water is removed.

  1. More

  2. Same

  3. Less

  4. None of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

False because the liquid displaced has the same weight as the wooden block has The weight of the displaced liquid from the vessel is same as the weight of the wooden block.
Hence,  the weight will remain the same.

Multiple choice archimedes' principle fluid pressure properties of matter physics

A sphere is floating in water its $\dfrac{1}3rd$ part is outside the water and when the sphere is floating in unknown liquid, it's $\dfrac {3}{4}th$ part is outside the liquid than the density of the liquid is

  1. $\dfrac{4}9\ gm/cc$
  2. $\dfrac{9}4\ gm/cc$
  3. $\dfrac{8}3\ gm/cc$
  4. $\dfrac{3}8\ gm/cc$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

volume of liquid inside the liquid1=2/3rd of total volume

volume of liquid inside the liquid2 = 1/4th of total volume

density of liquid= (2/3)/(1/4) = 8/3 g/cc

Multiple choice archimedes' principle fluid pressure properties of matter physics

A boat carrying steel balls is floating on the surface of water in a tank.If the balls are thrown into the tank one by one , how will it affect the level of water :

  1. It will remain unchanged

  2. It will rise

  3. It will fall

  4. First it will raise and then fall
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Since the weight remains constant & so does buoyant force on a floating body. Hence there will be no change in level of water.

Multiple choice archimedes' principle fluid pressure properties of matter physics

Choose the correct statement from the following:

  1. A body will sink in a liquid if its weight is equal to or greater than the weight of the liquid displaced by it

  2. A body will float in a liquid if its weight is equal to or less then the weight of liquid displaced by it

  3. When a body floats in a liquid, the portion of the body above the surface of the liquid is independent of the density of the body relative to that of the liquid

  4. In still air, a hydrogen filled balloon rises up to certain height and then stops rising.
Reveal answer Fill a bubble to check yourself
B,D Correct answer
Explanation
According to Archimedes
${ F } _{ b }=$weight of liquid displaced by object
The object floats if ${ F } _{ b }\ge mg$
Weight of liquid displace$\ge $ weight of object
When a body floats the portion immersed or above liquid is dependent on body's density.
The balloon rises till ${ F } _{ b }> mg$. Then stops, since ${ F } _{ b }$ decreases as air gets thin.
Multiple choice archimedes' principle fluid pressure properties of matter physics

Why an iron nail floats on mercury but it sinks in water?

  1. Density of iron is more than that of mercury, but less than that of water.

  2. Density of iron is less than that of mercury, but more than that of water.

  3. Density of iron is less than that of mercury and water

  4. Density of iron is more than that of mercury, water.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This is because density of mercury is more than that of water.
An object floats on a liquid, if its density is lower than that of the liquid. 
The density of iron nail is more than that of the water but less than that of mercury.

Multiple choice physics nuclei nuclear force the nuclear force nuclear force and binding energy

The binding energy per nucleon for $\mathrm { U } ^ { 238 }$ about 7.5Mev where as it is about 8.5 Mev for a nucleus having a mass half of Uranium. If $\mathrm { U } ^ { 238 }$ splits into two exact halves the energy released would be

  1. 6.4 Mev

  2. 119 Mev

  3. 238 Mev

  4. 476 Mev
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Energy released = (Total binding energy of products) - (Total binding energy of reactants). Reactants: 238 nucleons * 7.5 MeV = 1785 MeV. Products: 2 * (119 nucleons * 8.5 MeV) = 2023 MeV. Energy released = 2023 - 1785 = 238 MeV.

Multiple choice physics nuclei nuclear force the nuclear force nuclear force and binding energy

The excitation energy of a hydrogen like ion to first excited state is 40.8 eV. The energy needed to remove the electron from the ion the ground state is

  1. 54.4 eV

  2. 62.6 eV

  3. 72.6 eV

  4. 58.6 eV.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For a hydrogen atom like system the energy for $n^{th}  $ level is given by $E _n=\dfrac{-13.6Z^2}{n^2}eV$

So the ground state energy will be $E _1=\dfrac{-13.6Z^2}{1}eV$
and for the state $n=2$ the energy is $E _2=\dfrac{-13.6Z^2}{4}eV$
So the excitation energy foe this state will be $E _2 -E _1=10.2Z^2eV$
as it is given to be $40.8eV$  so $Z^2=4$ or $Z=2$
So the energy in ground state will be $E _1=-54.4eV$
so the inonization energy will be $-(-54.4eV)=54.4eV$

Multiple choice physics nuclei nuclear force the nuclear force nuclear force and binding energy

Identify the correct statement/statements:
a) At greater distances nuclear forces are negligible
b) Nuclear forces are non central forces
c) Nuclear forces are weakest in nature
d) Nuclear forces are charge dependent forces

  1. a, b

  2. b, c

  3. c, d

  4. a, d
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Nuclear forces properties :
1) They will act upto nearly one ferms. Beyond that they become negligible.
2) Charge independent : $F _{pp} = F _{pn} = F _{nn}$
3) They do not act along the line joining the centres of the nuclears, so they are non-central forces.
4) Nuclear forces are strong in nature.
So, correct choice is option A.