Tag: centre of gravity

Questions Related to centre of gravity

State whether given statement is True or False.

Centre of gravity of a freely suspended body always lies vertically below the point of suspension.

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

  1. True

  2. False

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Correct Option: A
Explanation:

Yes, Centre of gravity of a freely suspended body always lies vertically below the point of suspension. The center of gravity of an object is the point you can suspend the object from without there being any rotation because of the force of gravity, no matter how the object is oriented. If you suspend an object from any point, let it go and allow it to come to rest, the center of gravity will lie along a vertical line that passes through the point of suspension. Unless you've been exceedingly careful in balancing the object, the center of gravity will generally lie below the suspension point.

Where is the centre of gravity of a uniform ring situated ?

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

  1. At the centre of ring.

  2. At the centre of semicircular ring

  3. At the centre of radius

  4. cant say

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Correct Option: A
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 bodies centre of gravity lies at the centre of the body.Hence we know that there will be a centre for a uniform ring lamina.Hence this centre of the ring will be centre of gravity.

Stability and center of gravity of an object whose stability can be increased by

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

  1. lowering center of gravity and increasing area of base

  2. lowering center of gravity and decreasing area of base

  3. moving center of gravity higher and increasing areas of base

  4. moving center of gravity higher and decreasing area of base

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Correct Option: A
Explanation:

The position of the centre of gravity of an object affects its stability. The lower the centre of gravity is, the more stable the object. The higher it is the more likely the object is to topple over if it is pushed.
In general, increasing the size of the base (that is area) of support increases stability.

Centre of gravity of the circular ring will be:
physics turning effects of forces centre of gravity forces - vectors and moments acceleration due to gravity

  1. At the periphery

  2. At the center

  3. Outside it

  4. None

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Correct Option: B
Explanation:

Centre of gravity of the circle lies at its geometric centre because the resultant weight of the circle acts at its centre.

State whether true or false.
The position of the centre of gravity of the pot before filling it with water will be at its base.

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

  1. True

  2. False

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Correct Option: B
Explanation:

Before filling in with water the centre of gravity will be somewhere in the empty place in the pot.

An object can have 

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

  1. more than one center of gravity.

  2. only one center of gravity 

  3. always two center of gravity

  4. none of the above 

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Correct Option: B
Explanation:

Centre of gravity of an object is a specific point such that the body behaves as if the entire gravitational force is acting only at that point. It is unique for an object and can't be more than 1.

The centre of mass of a system of particles is at the origin. From this we conclude that :

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

  1. The numberof particles on positive x-axis is equal to the number of particles on negative x-axis

  2. The total mass of the particles on positive x-axis is same as the total mass on negative x-axis

  3. The number of particles on X-axis may be equal to the number of particles on Y-axis.

  4. If there is a particle on the positive X-axis, there must be at least one particle in the negative X - axis.:

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Correct Option: D
Explanation:
Given :  The COM of the system  is at origin   i.e  $X = 0$
Let the position of particle of mass $m _1$ on the positive axis be  $a$.
Using       $X = \dfrac{m _1x _1+m _2x _2}{m _1+m _2}$
$\therefore$   $0 = \dfrac{m _1a+m _2x _2}{m _1+m _2}$              $\implies x _2 = -\dfrac{m _1}{m _2}a$
This implies that for a particle on the positive X axis, there must be at least one particle particle in the negative X axis.

A book is lying on a table, what is the angle between the book on the table and the weight of the book?

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

  1. $0^o$

  2. $45^o$

  3. $90^o$

  4. $180^o$

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Correct Option: C
Explanation:

Weight always point towards the center of the earth that is perpendicular to the surface of the earth that is towards the table and $perpendicular$ to surface of the table.


Now as the book is lying on the table i.e. book is $parallel$ to the table and the weight is perpendicular to the table so the required angle is $90^0$
Option C is correct.

The center of gravity of an object 

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

  1. can never exist at a point where there is no mass.

  2. can exist at a point where there is no mass.

  3. may exist or may not exist.

  4. none of the above

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Correct Option: B
Explanation:

Centre of gravity of an object is a specific point such that the body behaves as if the entire gravitational force is acting only at that point. It is unique for an object and can't be more than 1.

There are some objects whose centre of gravity doesn't have any matter at it. Eg: A hollow sphere and a ring have their centres of gravity at their geometric centres. 

The centre of gravity of an object is ______ whether it is placed near the surface of the Earth or near the surface of the Moon.

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

  1. same 

  2. different 

  3. depend on the situation

  4. none

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Correct Option: A
Explanation:

Centre of mass is a point on a physical body which behaves as if the whole mass is concentrated over there. Whenever a force acts on a body it appears to be acting on the centre of mass. Whenever gravitational force is acting on a body it appears to be acting on a specific point on the body which is known as the centre of gravity.
 It usually coincides with the centre of mass. Earth being a larger planet than the moon, the gravitational force is more intense on earth as compared to the moon.
 The location of the centre of mass does not vary with the intensity of the force acting on the body. Similarly, centre of gravity does not vary with the intensity of the gravitational force acting on it.  Hence the centre of gravity on earth and moon will be the same