Physics · Science General

Newtonian Mechanics and Forces

1,605 Questions

Newtonian mechanics studies the motion of objects and the physical laws governing them. This hub covers friction, gravitational force, inertia, and vector quantities. Mastering these fundamental physics concepts is essential for various government competitive exams.

Laws of motionFriction and inertiaVector and scalar quantitiesGravitational accelerationArchimedes principle

Newtonian Mechanics and Forces Questions

Multiple choice physics electric fields introduction to electrostatic force electric force charging and discharging

An inflated balloon was pressed against a wall after it has been rubbed with a piece of synthetic cloth. It was found that the balloon sticks to the wall. What force might be responsible for the attraction between the balloon and the wall?

  1. Gravitational

  2. Magnetic

  3. Electrostatic

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

Electrostatic force is the phenomenon that results from slow-moving or stationary electrical charges. Specifically, electrostatic force is the physical reaction that holds together the electromagnetic field created by subatomic particles, such as electrons and protons. In order for electrostatic forces to remain cohesive, these particles need to independently maintain both positive and negative charges and react to each other accordingly. 
When a balloon is rubbed with a cloth, the electrons from the atoms of the cloth enter the atoms of the balloon and the number of electrons in the atoms of balloon becomes more than the number of protons. Because of that, there is a negative charge in the balloon, and in the cloth the number of electrons in its atoms become less than the number of protons, so it's positively charged.
Therefore, due to this electrostatic force, the balloon sticks to the wall.

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

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

  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
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

An object can have 

  1. more than one center of gravity.

  2. only one center of gravity

  3. always two center of gravity

  4. none of the above

Reveal answer Fill a bubble to check yourself
B Correct answer
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.

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

The center of gravity of an object 

  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
Reveal answer Fill a bubble to check yourself
B Correct answer
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. 

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

Center of gravity is usually located where

  1. less mass is concentrated

  2. less weight is concentrated

  3. more mass is concentrated

  4. more weight is concentrated
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

Since weight means the gravitational force acting, D is the correct option.
C is not the correct option because, for very large bodies like huge mountains, it is not at the point where more mass is concentrated

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

One can lean further to one side or the other without creating enough turning force to tip him over. This is because 

  1. The person has low centre of gravity

  2. The person has no centre of gravity

  3. The person has high centre of gravity

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

Center of gravity is the point at which the entire weight of a body may be considered as concentrated so that if supported at this point the body would remain in equilibrium.

One can lean further to one side or other without creating enough turning force to tip him over. This is because the person has low center of gravity as having a low center of gravity decreases the torque hence the person will not tip over.

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

What is the center of gravity of an object?

  1. The point where gravity appears to act.

  2. The point where gravity doesn't act.

  3. The point where the force of gravity is strongest.

  4. The point where the force of gravity is weakest.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Option A is the definition of the centre of gravity. B is a contradiction. As far as C ad D are concerned, the force of gravity is equal at all points provided the object is small as compared to the radius of the planet. 

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

Which one of following statements related to center of gravity is incorrect?

  1. The center of gravity of an object is defined as point through which its whole weight appears to act.

  2. The center of gravity is sometimes confused with center of mass.

  3. The center of gravity always lies inside object.

  4. For an object placed in a uniform gravitational field, center of gravity coincides with center of mass.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A is the proper definition. In some bodies like hollow bodies, frames and rings, the center of gravity is at the geometric centre where the matter of the object is not present.

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

The stability of a flexible body depends on:

  1. height of the center of gravity from the ground.

  2. base area of the body.

  3. shape of the body.

  4. all the above.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The stability of objects depends on the base, C.G and shape of the body. For a body to be the stable,

  1. The base of the body need to be broad.
  2. The Centre of gravity should be as low as possible.
  3. The vertical line through the center of gravity should fall within the base.

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

People can spin a ball on their finger. This is due to

  1. the centre of gravity of the ball is on his finger.

  2. the resultant force is passing through the centre of gravity of the ball.

  3. the resultant force is passing through the centre of the ball.

  4. both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

let us assume body of mass m and divide it into many small particles. The centre of mass means it is the mean value of the all the small particles . it would more clear by assuming the body in 3-D coordinate system and calculate its mean of all small particles with the co ordinates in three dimension . where as the centre of gravity is also same but it is the mean of its weight. it is the point were total weight acts


we may think  both be same but not always. because in above example the value of g will be different at different positions because of that while calculating the mean the centre will shifts from centre of mass


in the question given the centre of mass will be exact center of ball and centre of gravity also lies at the center of mass as the ball is small there will be no greater effect by g. so the the centre of gravity of ball is on finger and resultant force is weight which is all acts on center of ball

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

If we suspend lamina at different positions, its center of gravity will still lie along the :

  1. plumb line

  2. line of force

  3. line of weight

  4. gravity line
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

let us assume body of mass m and divide it into many small particles. The centre of mass means it is the mean value of the all the small particles . it would more clear by assuming the body in 3-D coordinate system and calculate its mean of all small particles with the co ordinates in three dimension . where as the centre of gravity is also same but it is the mean of its weight. it is the point were total weight acts

we may think  both be same but not always. because in above example the value of g will be different at different positions because of that while calculating the mean the centre will shifts from centre of mass 
  because  suspension of the body at the different position the value of g value effects at some point so the centre of gravity will shifts but stays along blub line



Multiple choice physics turning effects of forces centre of gravity forces - vectors and moments acceleration due to gravity
Around the centre of gravity ______ vanishes. Fill in the blank. 

  1. Resultant acceleration due to gravity force

  2. Resultant velocity due to gravity force

  3. Resultant torque due to gravity force

  4. None
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Resultant torque due to gravity force vanishes around the centre of gravity because perpendicular distance between the gravitational force and the point about that toque is calculated becomes very very small or almost zero.