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

An object will not undergo rotational motion when:

  1. the forces are acting on it at different positions

  2. every forces is creating different turning effects

  3. every moment has the same amplitude

  4. all the forces are acting at its centre of gravity
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

For an object to undergo rotational motion, a net torque must be exerted on the object. If all the forces are acting at its centre of gravity, net torque acting on the object is zero and so the object will not undergo any rotational motion.

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

An object after deforming 

  1. may have different centre of mass.

  2. have same centre of mass

  3. doesn't change its centre of gravity

  4. none of the above

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

The centre of mass depends upon how the particles of the body are scattered around it. It is closer towards the heavier regions of the body as compared to the lighter regions.  Whenever an object is deformed, its heavier regions may change their locations. As a result, the centre of mass may change its location

Multiple choice physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

Mark the correct option

  1. The state of motion of an object is described by its speed only

  2. Many a time application of force does not result in a change in the state of motion of an object

  3. By sitting on a bicycle seat force is applied to the spring fixed to the seat of a bicycle

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
$(i)$ option $A$ is correct, as if to know about the unifomity of a motion and the body is moving or not speed is used as the parameter
$(ii)$Option B is correct, as the acceleration of a body depends on the net force a applied not on single $10r$ individual forces.
$(iii)$ Option $C$ is correct, while sifting on the bicycle, the spring force allached to the seat balances weight.
Option $D$ 

Multiple choice physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

Newton's law of motion cannot be applicable to the particle moving at a speed comparable to the speed of

  1. $Light$
  2. $Sound$
  3. $Rocket$
  4. $Bullet train$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Newton's law of motion are applicable for matter which occupy some space and have some mass. It is not possible for any matter to travel with speed of light. Secondly the mass charges as the speed approaches speed of light. Newton's law is applicable only when mass is constant so light is correct option.

Multiple choice physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

Choose the correct statement(s)

  1. Motion necessarily takes place along the direction of force

  2. If no force acts, the body is at rest

  3. A body in motion, need not be acted upon by a force

  4. A change in speed is always there, whenever a force is applied on the moving body
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Motion always takes place along velocity of the body.So it does not necessarily takes place along the direction of force.
When a body moves with uniform velocity , there is no force acting on the body. So option B is incorrect and C is correct.
We know that magnetic force does not do work. It can change the direction of motion but never change the speed. So option D is incorrect.

Multiple choice physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

A ball moving on a table top eventually stops. What is the reason ?

  1. due to gravity.

  2. due to friction between the ball and table

  3. due to other external force.

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

Due to the force of friction between the ball and table top, it  opposes the motion of the ball. And, gradually its speed keeps on decreasing and the ball finally stops.

Multiple choice physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

Object will remain at rest or in uniform motion in a straight line unless acted upon by an external force - which law is this ?

  1. Newton's third law

  2. Newton's first law

  3. Newton's second law

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

Statement of Newton's first law of motion,

It states that a body will remain at rest or in state of motion unless an external force is applied to the object.
To have any changes in state of object , force is necessary.

Multiple choice physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

The acceleration produced in a body by a force of given magnitude depends on:

  1. size of the body

  2. shape of the body

  3. mass of the body

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

Newton's second law of motion, $F=ma$, where $m$ is mass of an object which acquires acceleration $a$ when force $F$ is applied on it.
For a force of constant magnitude, $a\propto{\dfrac{1}{m}}$ i.e. acceleration is inversely proportional to mass.

Multiple choice physics force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

An object moving at constant velocity must:

  1. have a net force on it

  2. eventually stop due to gravity

  3. not have any force of gravity on it

  4. have zero net force on it
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The object moving with constant velocity must have zero acceleration i.e. $a _{net} = 0$. From Newton's IInd law the net external force must be zero in case of zero acceleration.

Net external force acting on the object  $F _{net} = ma _{net} = 0$
Hence answer D is correct.