Tag: physics

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Questions Related to physics

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

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

  1. ${ 10 }^{ -2 }N$
  2. ${ 10 }^{ -3 }N$
  3. $2\times { 10 }^{ -3 }N$
  4. $zero$
Reveal answer Fill a bubble to check yourself
D Correct answer
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 $=ma=0$.

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

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

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.