Physics · Science General

Newtonian Mechanics and Forces

1,559 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 force and newton's laws of motion first law of motion newton's first law of motion momentum and newton's laws

Newtons law are not valid in

  1. Both inertial as well as non- inertial frame of reference.

  2. A frame moving with constant velocity w.r.t. an inertial frame.

  3. All reference frames which are at rest w.r.t. an inertial frame.

  4. The reference frame attached to the earth.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Newton's Law is only valid in inertial frame of reference. If there is a non - inertial frame of reference then it won't be valid. 

Hence option $\textbf A$ is the correct answer.

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 force vector applied on a mass is represented by $\vec {F} = 6\hat {i} - 8\hat {j} + 10\hat {k}$ and accelerates with $1\ m/s^{2}$. What is the mass of the body?

  1. $14\ kg$
  2. $10\sqrt {2}kg$
  3. $2\sqrt {10}kg$
  4. $20\ kg$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
To find mass of the body we will use magnitude of force formula $,$ 
According to question$:-$
$\overrightarrow { F } =6-8\widehat { j } +10\widehat { k } $
Magnitude of Force $=\sqrt {\left( {{6^2} + {8^2} + {{10}^2}} \right)} $
                                  $= 14.14 N$
$m = F / a$
     $= 14.14 N / 1 m/s^2$
     $= 14.14 kg$
Hence,
option $(A)$ is correct answer.
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

Statement 1 : There can be displacement of an object even in the absence of any force acting on it.
Statement 2 : An object in uniform motion in a straight line shows displacement even when the net force acting on it is zero.

  1. Both statement 1 and statement 2 are true and statement 2 is correct explanation of statement 1

  2. Both statement 1 and statement 2 are true, but statement 2 is not correct explanation of statement 1

  3. Statement 1 is true but statement 2 is false

  4. Statement 1 is false but statement 2 is true
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Answer is A.

If any body is in the state of rest or in uniform motion, it remains in that state until an external force is applied on it. 
So, if a body is initially moving with some constant velocity, it can continue to move with same velocity even if no external force is acting on it.
In fact, the effect of force is to accelerate and not just displace. For example, an object moving straight in space far away from any celestial objects will continue to move forever, although there is no force acting on it. This is due to Newton's first law of motion or law of inertia.
Hence, Both statement 1 and statement 2 are true and statement 2 is correct explanation of statement 1.

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

While dusting a carpet, we give it a sudden jerk or beat it with a stick because: 

  1. the inertia of rest keeps the dust in its position and the dust is removed when the carpet moves away.

  2. the inertia of motion removes dust.

  3. no inertia involved in process.

  4. jerk compensates for the force of adhesion between dust and carpet and dust is removed.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

While dusting we give a sudden serk our beat with stick because when we do that stick because when we do that the particle of carpet move with our help and the dust particle stays at rest by inertia and eventually they separate from the carpet.

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

Inertia is the property of a body which preserves its state of motion or uniform motion in a straight line. The following factors tell me about inertia.
I. Greater the mass of a body, greater is its inertia.
II. Greater the inertia of a body, the less will be the acceleration produced by a given force.
III. The law of inertia is the same as Newton's first law of motion. 
Which combination is true?

  1. I and III only

  2. I and II only

  3. I, II and III

  4. II and III only
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

All three statements are standard definitions and properties related to inertia and Newton's first law of motion.

Multiple choice physics oscillations a few applications of linear shm simple pendulum example of simple harmonic motion

A planck with a body of mass m placed on to it starts moving straight up with the law $y=a(1-\cos{\omega t})$ where $\omega$ is displacement. Find the time dependent force:

  1. $-ma\omega^2\cos{\omega t}$
  2. $ma\omega^2\cos{\omega t}$
  3. $ma\omega^2\sin{\omega t}$
  4. $mg+ma\omega^2\cos{\omega t}$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Total force on the particle will be
$F=mg+m\dfrac { d^{ 2 }y }{ dt^{ 2 } } $
since $y=a(1-\cos { \omega t } )\\ \Rightarrow \dfrac { dy }{ dt } =a\omega \sin { \omega t } \\ \Rightarrow \dfrac { d^{ 2 }y }{ dt^{ 2 } } =a\omega ^{ 2 }\cos { \omega t } $
$\Rightarrow F=mg+ma\omega ^{ 2 }\cos { \omega t } $

Multiple choice physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

A body is falling freely under the action of gravity alone in vacuum. Which of the following quantities remain constant during the fall?

  1. Kinetic energy

  2. Potential energy

  3. Total mechanical energy

  4. Total linear momentum
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
As the body is falling freely under gravity, the potential energy decreases continuously and kinetic energy increases continuously as all the conservative forces are doing work. So, total mechanical energy $(PE + KE)$ of the body will be constant.
At point A total mechanical energy will be $EA = K.E + P.E$
$E _{A}=\dfrac{1}{2}mv^{2}+m _{g}H$
As velocity will be zero at $A$, so its kinetic energy will be zero 
$E _{A}=M _{g}H$
Velocity at point $B$ will be 
$V _{B}=\sqrt{2gh}$
So energy at point $B$ will be 
$E _{B}=KE+PE$
$E _{B}=\dfrac{1}{2}m(2gh)+mg(H-h)$
$E _{B}=mgh+mgH-mgh$
$E _{B}=mgH$
Now velocity at point $C$ will be 
$V _{C}=\sqrt{2gh}$
So energy at point $C$ will be
$ E _{C}=KE+PE$
$E _{C}=\dfrac{1}{2}m(2gH)+mg(0)$
So, total mechanical energy will remain same (if we neglect the air friction).
Multiple choice physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

While falling

  1. Potential energy

  2. Kinetic energy

  3. Both A & B

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

While it is falling it has certain velocity,as kinetic energy is defined as the virtue of its state of motion it will have kinetic energy.As it is at certain height it will have Potential energy which is defined by virtue of state of its position.Hence ball has both potential and kinetic energy.

Multiple choice physics types of energy renewable and non-renewable resources renewable and non-renewable sources of energy substances, objects and energy

Identify an example of kinetic mechanical energy?

  1. A loaded gun

  2. A set mouse trap

  3. An elevated wrecking ball

  4. A compressed spring

  5. A bike rolling down a hill
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

A loaded gun, a set mouse trap and a compressed spring are examples of elastic potential energy.

An elevated wrecking ball is an example of gravitational potential energy.
A bike rolling down a hill is an example of kinetic energy, where potential energy is constantly converting in the kinetic energy of the bike as given by $\dfrac{1}{2}mv^2$.