Tag: physics

Questions Related to physics

When a glass rod is rubbed with silk, both become charged due to:

physics static electricity explaining static electricity charging by induction electric charges and fields

  1. migration of protons

  2. exchange of electrons and protons

  3. migration of electrons

  4. migration of neutrons

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Correct Option: C
Explanation:

When a glass rod is rubbed with silk cloth glass rod becomes positively charges while silk cloth becomes negatively charged. This is due to transfer or migration of electrons from glass rod to silk cloth.

A glass rod when rubbed with silk cloth acquires a charge $1.6 \times 10^{-13}  C$. What is the charge on the silk cloth?

physics static electricity explaining static electricity charging by induction electric charges and fields

  1. $-1.6 \times 10^{-19} C$

  2. $1.6 \times 10^{-13} C$

  3. $-1.6 \times 10^{-13} C$

  4. $1.6 \times 10^{-19} C$

Show answer
Correct Option: C
Explanation:

When a glass rod is rubbed with silk, both gets electrified due to charging by friction. Given, glass rod acquires positive charge $=1.6\times 10^{-31}\, C$. So silk acquires equal and opposite charge as that on glass rod. Hence the answer is $-1.6\times 10^{-13}\, C$.

For an astronaut in a spaceship, the sky appears

physics option d: astrophysics the big bang and the early development of the universe origin of universe evolution of the universe

  1. white

  2. black

  3. green

  4. blue

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Correct Option: B

The Hubble Deep Field is an image of the sky taken with a very along exposure, using the Hubble Space Telescope. Almost all of the $5000$ objects seen in that picture are?

physics option d: astrophysics the big bang and the early development of the universe origin of universe evolution of the universe

  1. Starts that are in our own Galaxy.

  2. Dirt on the lens of the telescope.

  3. Galaxies

  4. Distant planets.

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Correct Option: C

Can the centre of gravity be situated outside the material of the body ?

physics forces - vectors and moments centre of gravity turning effects of forces acceleration due to gravity

  1. Yes

  2. No

  3. Can't say

  4. None

Show answer
Correct Option: A
Explanation:

Yes, it can. For example, in case of a ring, it is situated at the centre of that circle. But the material is only along the circumference. Hence centre of gravity is situated outside the material of the body.

Reference to ability of an object to return to its original position after it has been tilted slightly is termed as:

physics forces - vectors and moments centre of gravity turning effects of forces acceleration due to gravity

  1. Stability

  2. Equilibrium

  3. Centre of gravity

  4. Torque

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Correct Option: A
Explanation:

stability of an object depends on the ability of an object to return back to its original equlibirum, when disturbed

If you place pivot at center of a meter rule, weight has no

physics forces - vectors and moments centre of gravity turning effects of forces acceleration due to gravity

  1. property

  2. Concern

  3. Turning effect

  4. Magnitude

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Correct Option: C
Explanation:

The weight of an object is concentrated at the centre of gravity and hence a pivot at the centre of the metre scale does not record any changes in mass. Hence the scale does not turn around

What is the position of centre of gravity of a cylinder?

physics motion of system of particles and rigid bodies centre of gravity turning effects of forces forces - vectors and moments

  1. At the center of base circle

  2. At the center of top circle

  3. Cannot be determined

  4. At the mid point on the axis of cylinder

Show answer
Correct Option: D
Explanation:

Centre of gravity means a point from which the weight of a body or system may be considered to act. In uniform gravity it is the same as the centre of mass. For regular shaped bodies it lies at the centre of the that particular body. Hence for a cylinder centre of gravity lies at the midpoint of the axis of the cylinder.

In an artificial satellite, the use of a pendulum watch is discarded, because :

physics motion of system of particles and rigid bodies centre of gravity turning effects of forces forces - vectors and moments

  1. The satellite is in a constant state of motion

  2. The effective value of $g$ becomes zero in the artificial satellite

  3. The periodic time of the pendulum watch is reduced

  4. None of these

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Correct Option: B

Given that there is a relationship between the orbital radius of a planet and its period of revolution and that the periods of revolution of Mercury, Earth, Jupiter and Neptune and nearly 0.24, 1, 11.8 and 165 years. It follows that the period of revolution of
1. Venus is less than 0.24 years
2. Mars is less than 12 years
3. Uranus is more than 165 years
4. Uranus is less than 165 years but more than 12 years.

physics motion of system of particles and rigid bodies centre of gravity turning effects of forces forces - vectors and moments

  1. 1 and 3

  2. 4 only

  3. 3 o nly

  4. 2 and 4

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Correct Option: D