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 rotational motion of a rigid body and moment of inertia angular momentum (l) and conservation of angular momentum angular momentum in case of rotation about a fixed axis law of conservation of angular momentum

Under the action of a central force, there is a conservation of-

  1. Angular momentum only

  2. Mechanical energy only

  3. Angular momentum and mechanical energy

  4. Neither angular momentum nor mechanical energy
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Under the action of a central force, there is a conservation ofAngular momentum and mechanical energy.

Multiple choice physics rotational motion of a rigid body and moment of inertia angular momentum (l) and conservation of angular momentum angular momentum in case of rotation about a fixed axis law of conservation of angular momentum

The angular momentum of a system of particles is conserved 

  1. When no external force acts upon the system

  2. When no external torque acts upon the system

  3. When no external impulse acts upon the system

  4. none of these

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

Angular momentum is conserved when the net external torque acting on a system is zero. This is the rotational analog to the conservation of linear momentum, which occurs when the net external force is zero.

Multiple choice physics rotational motion of a rigid body and moment of inertia angular momentum (l) and conservation of angular momentum angular momentum in case of rotation about a fixed axis law of conservation of angular momentum

If no external force acts on a system

  1. Velocity of centre of mass remains constant

  2. Total kinetic energy of the system remains constant

  3. Angular momentum of system may change

  4. Total mechanical energy of the system remains constant
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

No force means no acceleration implying constant velocity. Also as velocity is constant kinetic energy remains constant. The angular momentum may change due to the change in moment of inertia. Also the total mechanical energy may change due the change in potential energy.

Multiple choice physics rotational motion of a rigid body and moment of inertia angular momentum (l) and conservation of angular momentum angular momentum in case of rotation about a fixed axis law of conservation of angular momentum

Angular momentum of a system a particles changes, when

  1. Force acts on a body

  2. Torque acts on a body

  3. Direction of velocity changes

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

If we apply a torque on a body, then angular momentum of the body changes according to the relation
$\bar{\tau} = \displaystyle\frac{d\bar{L}}{dt} \Rightarrow if \space \bar{\tau} = 0$ then, $\overrightarrow{L} = constant$

Multiple choice physics rotational motion of a rigid body and moment of inertia angular momentum (l) and conservation of angular momentum angular momentum in case of rotation about a fixed axis law of conservation of angular momentum

A gymnast takes turns with her arms & legs stretched. When she pulls her arms & legs in

  1. The angular velocity decreases

  2. The moment of inertia decreases

  3. The angular velocity stays constant

  4. The angular momentum increases
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Since no external torque act on gymnast, so angular momentum $(L =

I\omega)$ is conserved. After pulling her arms & legs, the angular velocity increases but moment of inertia of gymnast, decreases in, such a way that angular momentum remains constant.

Multiple choice physics rotational motion of a rigid body and moment of inertia angular momentum (l) and conservation of angular momentum angular momentum in case of rotation about a fixed axis law of conservation of angular momentum

If a running boy jumps on a rotating table, which of the following is conserved?

  1. Linear momentum

  2. K.E

  3. Angular momentum

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

The boy does not exert a torque to rotating table by jumping, so angular momentum is conserved i.e., 
$\displaystyle\frac{d\bar{L}}{dt} = 0 \Rightarrow \bar{L} = constant$

Multiple choice physics rotational motion of a rigid body and moment of inertia angular momentum (l) and conservation of angular momentum angular momentum in case of rotation about a fixed axis law of conservation of angular momentum

A body is moving on a rough horizontal plate in a circular path being tide to a nail (at the centre) by a string, while the body is in motion the friction force of the body

  1. changes direction

  2. changes magnitude

  3. changes both magnitude and direction

  4. none of he above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

As the motion is circular, friction opposes the centripetal acceleration, thus its direction changes regularly.

Multiple choice

Which law states that all objects attract each other through gravitational force?

  1. Law of Universal Attraction

  2. Law of Universal Gravitation

  3. Law of Acceleration

  4. Law of Conservation of Energy
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The Law of Universal Gravitation states that every particle of matter in the universe attracts every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.