Tag: physics

Questions Related to physics

 A person in a car tends to fall back when it suddenly starts. It is due to

physics along with motion motion around us motion and rest moving things around us

  1. Inertia of rest

  2. Inertia of motion

  3. Inertia of direction

  4. none

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Correct Option: A
Explanation:

when bus suddenly start moving in forward direction. This happens due to. When a bus suddenly starts, the standing passengers fall backward in the bus.

It is due to inertia of rest.
Hence,

option $A$ is correct answer.

The wall of your classroom is in a state of -

physics along with motion motion around us motion and rest moving things around us

  1. motion

  2. rest

  3. neither rest nor motion

  4. none of these

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Correct Option: B
Explanation:

The walls are at rest with respect to the Earth. When you are sitting in the classroom, you are also at rest with respect to the Earth, and so the walls do not seem to be moving to you.

If the forces acting on an object are balanced, then_____

physics along with motion motion around us motion and rest moving things around us

  1. the object will be in equilibrium

  2. the object will be in motion

  3. the object will have zero acceleration

  4. the object loses its shape

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Correct Option: A,C
Explanation:

according to newton's first law of motion, an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

so if forces acting on the object is balanced then the object will be in equilibrium and it will not have any acceleration.
cannot comment about option B because if initially object is at rest then it will be always at rest .
so best possible answer are option A,C.

If $\vec {u}=a \hat {i}+b \hat {j}+ c \hat {k}$ with $\hat {i},\hat {j},\hat {k}$ are in east, north and vertical directions, the maximum height of the projectile is ?

physics along with motion motion around us motion and rest moving things around us

  1. $\dfrac{a^{2}}{2g}$

  2. $\dfrac{b^{2}}{2g}$

  3. $\dfrac{c^{2}}{2g}$

  4. $\dfrac{b^{2} c^{2}}{2g}$

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Correct Option: C

If the energy density and velocity of a wave are $u$ and $c$ respectively then the energy propagating per second per unit area will be

energy in wave motion oscillation and waves waves physics

  1. $u/c$

  2. $c^2u$

  3. $uc$

  4. $c/u$

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Correct Option: C
Explanation:

If the energy density and velocity of a wave are $u$ and $c$ respectively then the energy propagating per second per unit area will be $uc.$

The kinetic energy per unit length for a wave on a string is the positional coordinate

energy in wave motion oscillation and waves waves physics

  1. True

  2. False

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Correct Option: B
Explanation:

The kinetic energy for a particle is given by $(\mu \Delta x/ 2) (\dfrac{dy}{dt})^2$

Thus, it depends only on the time variable and not on the position variable

A travelling wave has an equation of the form $A(x,t)=f(x+vt)$. The relation connecting positional derivative with time derivative of the function is:

energy in wave motion oscillation and waves waves physics

  1. $\dfrac{dA}{dt}=\pm v^2 \dfrac {dA}{dx}$

  2. $\dfrac{dA}{dt}=\pm v \dfrac {dA}{dx}$

  3. $\dfrac{dA}{dt}=\pm \sqrt(v) \dfrac {dA}{dx}$

  4. $\dfrac{dA}{dt}=(2 \pi v/\lambda) \dfrac {dA}{dx}$

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Correct Option: B
Explanation:

Positional derivative and time derivative of a function f is $\dfrac{dA}{dt}=\pm v \dfrac {dA}{dx}$

The correct option is (b)

Kinetic energy per unit length for a particle in a standing wave is zero at:

energy in wave motion oscillation and waves waves physics

  1. nodes

  2. antinodes

  3. mid-way between a node and an antinode

  4. None of the above

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Correct Option: B
Explanation:

Particle at antinodes is momentarily at rest and hence has zero kinetic energy. Its speed comes down to zero at this point and all energy is stored in the form of potential energy.

The total energy per unit length for a travelling wave in a string of mass density $\mu$ , whose wave function is $A(x,t) = f(x \pm vt)$ is given by: 

energy in wave motion oscillation and waves waves physics

  1. $E _tot = \sqrt(\mu/2) (\dfrac{dA}{dt})^2$

  2. $E _tot = (\mu/2) (\dfrac{dA}{dt})^2$

  3. $E _tot = (\mu/2)^2 (\dfrac{dA}{dt})^2$

  4. $E _tot = (2\mu) (\dfrac{dA}{dt})^2$

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Correct Option: B

The maximum potential energy / length increases with:

energy in wave motion oscillation and waves waves physics

  1. Amplitude

  2. Wavelength

  3. Frequency

  4. Velocity

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Correct Option: C
Explanation:

If $y= A \sin (\omega t- kx)$ is the equation of a wave through a string, then the slope of the wave is $\dfrac{dy}{dx}=- Ak \cos (\omega t- kx)$. 

The maximum potential energy will be $T \times \Delta x \times (\dfrac{dy}{dx})^2A^2k^2=A^2k^2 \cos ^2(\omega t -  kx)T \Delta x$

The maximum potential energy will be obtained if cos (\omega t - kx)=1. Thus, maximum potential energy = $4 \pi^2A^2T f \times T \times \Delta x $; T is the tension in the string

We also know that $T=\mu v^2$. Substituting, we get, 

Maximum potential energy = $4 \pi^2 f^2A^2 \mu$
Thus maximum potential energy depends on frequency and as frequency increases, potential energy also increases

The correct option is (c)