Tag: physics

Questions Related to physics

Restoring force in the SHM is

force in shm oscillations oscillation and waves physics

  1. conservative

  2. nonconservative

  3. frictional

  4. centripetal

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Correct Option: A
Explanation:

A conservative force is a force with the property that the work done in moving a particle between two points is independent of the taken path. Restoring force $F=kx,$ is such kind of force and is conservative.

In SHM, select the wrong statement, where ${F}$ is the force, ${a}$ is the acceleration and ${v}$ is the velocity of the particle in SHM.

force in shm oscillations oscillation and waves physics

  1. $\overset{\rightarrow}{F}\times \overset{\rightarrow}{v}$  is a null vector

  2. $|\overset{\rightarrow}{F}\times \overset{\rightarrow}{a}|=0$ (always)

  3. $\overset{\rightarrow}{F}\times \overset{\rightarrow}{a}< {0}$

  4. $\overset{\rightarrow}{a}.\overset{\rightarrow}{x}<0$

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Correct Option: C
Explanation:

The velocity, acceleration and thus the force are along the direction of motion in the SHM.

So the cross product of Force with velocity or acceleration is always zero.
Thus $A$ and $B$ are correct.
Also, acceleration is always in opposite direction to the displacement vector. So dot-product of acceleration and displacement is always negative. Thus $D$ is also correct.
$C$ is the wrong statement as the cross product of force and acceleration is strictly zero, because, $F=ma\Rightarrow ma\times a=0$.

A coin is placed on a horizontal platform, which undergoes horizontal simple harmonic motion about a mean position $O$.The coin does not slip on the platform. The force of friction acting on the coin is $F$.

force in shm oscillations oscillation and waves physics

  1. $F$ is always directed towards $O$

  2. $F$ is directed towards $O$ when the coin is moving away from $O$, and away from $O$ when the coin moves towards $O$

  3. $F=0$ when the coin and platform come to rest momentarily at the extreme position of the harmonic motion.

  4. $F$ is maximum when the coin and platform come to rest momentarily at the extreme position of the harmonic motion.

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Correct Option: A

The net external force acting on the disc when its centre of mass is at displacement $x$ with respect to its equilibrium position is:

force in shm oscillations oscillation and waves physics

  1. $-kx$

  2. $-2kx$

  3. $-\dfrac{2kx}{3}$

  4. $\dfrac{4kx}{3}$

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Correct Option: D

A particle is in S.H.M of amplitude $ 2$ cm. At extreme position the force is $4$N. At the point mid-way between mean and extreme position, the force is :

force in shm oscillations oscillation and waves physics

  1. $1$ N

  2. $2$N

  3. $3$N

  4. $4$N

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Correct Option: B
Explanation:

Amplitude = 2 cm
Force = 4N
$F = mw^{2}A=4$
$F _{1} = mw^{2}x$

Since $F$ is directly proportional to $x$ so , at midpoint the force when the amplitude is $2 \ cm$ will be $2N$

A 1 kg mass executes SHM with an amplitude 10 cm, it takes $2\pi$ seconds to go from one end to the other end. The magnitude of the force acting on it at any end is :

force in shm oscillations oscillation and waves physics

  1. 0.1 N

  2. 0.2 N

  3. 0.5 N

  4. 0.05 N

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Correct Option: A
Explanation:

As $  w  = \cfrac{2\pi}{T} = 1 \ rad/sec $ ;    Amplitude  $A  = 0.1 m$
magnitude of  force $ = m \times w^{2}.A$
                                  $=  0.1 N$

An elastic ball of density $d$ is released and it falls through a height $h$ before striking the surface of liquid of density $\rho(d < \rho)$. The motion of ball is:

force in shm oscillations oscillation and waves physics

  1. Periodic

  2. S.H.M.

  3. Circular

  4. Parabolic

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Correct Option: A

A body of mass 1/4 kg is in S.H.M and its displacement is given by the relation $y= 0.05 sin(20t+\dfrac{\pi }{2})$ m. If $t$ is in seconds, the maximum force acting on the particle is:

force in shm oscillations oscillation and waves physics

  1. $5$ N

  2. $2.5$ N

  3. $10$ N

  4. $0.25$ N

Show answer
Correct Option: A
Explanation:

$F= m\omega^{2}A$
$\omega = 20   rad / sec$
$A =   0.05   m$
Thus
$F= \dfrac{1}{4}\times 20\times 20\times \dfrac{1}{20}$
$=5 N $

A satellite of mass $m$ revolving around the earth in a circular orbit of radius $2R$ has to be shifted to another circular orbit of radius $4R$. The energy required for this process will be ($M\rightarrow$ mass of earth, $R\rightarrow$ radius of the earth)

physics search of life outside earth space research and satellites artificial satellites space missions and artificial satellites

  1. $\dfrac {GMm}{8R}$

  2. $\dfrac {2GMm}{3R}$

  3. $\dfrac {GMm}{4R}$

  4. $\dfrac {GMm}{6R}$

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Correct Option: A

The first Indian built rocket was launched from:

physics search of life outside earth space research and satellites artificial satellites space missions and artificial satellites

  1. Bangalore

  2. Sriharikota

  3. Thumba

  4. Trivandrum

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Correct Option: C
Explanation:

The first Indian built rocket was launched from Thumba on the outskirts of thiruvananthpuram on November 21 1963.