Tag: physics

Questions Related to physics

Newtons law are not valid in

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

  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.

Show answer
Correct Option: A
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.

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?

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

  1. $14\ kg$

  2. $10\sqrt {2}kg$

  3. $2\sqrt {10}kg$

  4. $20\ kg$

Show answer
Correct Option: A
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.

A force is not required to keep a body in a 

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

  1. Uniform circular motion

  2. Simple harmonic motion

  3. Motion with constant acceleration

  4. Motion with constant velocity

Show answer
Correct Option: D
Explanation:

If force on any body is zero than its acceleration should be zero that means its velocity would remain constant.

Which of the following is different from others?

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

  1. watt-sec

  2. coulomb-volt

  3. newton-metre

  4. coulomb-frarad

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Correct Option: D

A rain drop of mass $0.1g$ is falling with uniform speed of $10{ cm/s }$. What is the net force the drop?

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

  1. ${ 10 }^{ -2 }N$

  2. ${ 10 }^{ -3 }N$

  3. $2\times { 10 }^{ -3 }N$

  4. $zero$

Show answer
Correct Option: D
Explanation:

Uniform speed means that a body is traveling at a constant speed along a straight line. So it has no acceleration. Thus net weight $=ma=0$.

A car driver going at a speed v suddenly find a wide wall at a distance. (coefficient of friction is $\mu $) 

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

  1. If the apply breaks, he will come to rest after a distance $\dfrac { { { v }^{ 2 } } }{ 2\mu g } $

  2. If he turn the cart in a circle to avoid hitting, then radius of the circle is $\dfrac { { { v }^{ 2 } } }{ \mu g } $

  3. It is better to apply breaks rather than to turn the vehicle in a circle

  4. It is better to turn the vehicle in a circle than to apply brakes

Show answer
Correct Option: B
Explanation:

If he turn the cart in a circle to avoid hitting then radius of the circle is $\dfrac{{{v^2}}}{{2\mu g}}$
Option $B$ is correct answer.

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.

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

  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

Show answer
Correct Option: A
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.

Newton's law of motion were published in the year 1699:

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

  1. True

  2. False

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Correct Option: B
Explanation:

Newton's laws of motion published in $1687$ by the scientist $Issac$ $Newton$ in his Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy).

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

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

  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.

Show answer
Correct Option: A
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.

Physical independence of force is a consequence of:

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

  1. Newton's third law of motion

  2. Newton's second law of motion

  3. Newton's first law of motion

  4. All of these

Show answer
Correct Option: C
Explanation:

Newton''s first law of motion is related to physical independence of force.

Hence,
option $C$ is correct answer.