Tag: option b: engineering physics

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Questions Related to option b: engineering physics

Multiple choice physics option b: engineering physics introduction to sound free, forced and damped oscillations resonance

In damped oscillation mass is $1\ kg$ and spring constant $=100\ N/m$, damping coefficeint$=0.5\ kg\ s^{-1}$. If the mass displaced by $10\ cm$ from its mean position then what will be the value of its mechanical energy after $4$ seconds?

  1. $0.67\ J$
  2. $0.067\ J$
  3. $6.7\ J$
  4. $0.5\ J$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Given,

Mass, $m=1\,kg$

Spring constant, $k=100\,N/m^2$

Damping coefficient, $b=0.5\,kg/s$

Distance, $x=10\,cm$

Time, $t=4\,s$

We know,

The energy for damped oscillation, $E=\dfrac 12kx^2 e^{-\dfrac{bt}{m}}$

$E=\dfrac 12\times 100\times 0.01\times e^{-\dfrac{0.5\times 4}{1}}$

$E=\dfrac{e^{-2}}{2}=0.067\,J$

Hence the mechanical energy is $0.067\,J$
Multiple choice physics option b: engineering physics introduction to sound free, forced and damped oscillations resonance

In reality, a spring won't oscillate for ever.               will                the amplitude of oscillation until eventually the system is at rest.

  1. Frictional force, increase

  2. Viscous force, decrease

  3. Frictional force, decrease

  4. Viscous force, increase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In reality, a spring won't oscillate forever. Frictional force will decrease the oscillation until eventually, the system is at rest.

Multiple choice physics option b: engineering physics introduction to sound free, forced and damped oscillations resonance

Undamped oscillations are practically impossible because

  1. there is always loss of energy.

  2. there is no force opposing friction.

  3. energy is not conserved in such oscillations.

  4. None of these.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Underdamped oscillation is practical because there always be resistive force present in reality which will try to make an oscillating body to lose its energy. This loss of energy makes the motion damped motion.

Multiple choice physics option b: engineering physics introduction to sound free, forced and damped oscillations resonance

If we wish to represent the equation for the position of the mass in terms of a differential equation, which one of these would be the most suitable?

  1. $ m \dfrac{d^2x}{dt^2} + b \dfrac{dx}{dt} + kx = 0$
  2. $ m \dfrac{d^2x}{dt^2} - b \dfrac{dx}{dt} + kx = 0$
  3. $ m \dfrac{d^2x}{dt^2} + b \dfrac{dx}{dt} - kx = 0$
  4. $ m \dfrac{d^2x}{dt^2} -b \dfrac{dx}{dt} - kx = 0$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The force on body oscillating in resistive medium is 

$f = -kx - bv$
$\Rightarrow m\dfrac { { d }^{ 2 }x }{ d{ t }^{ 2 } } =-kx-b\dfrac { dx }{ dt } \ \Rightarrow m\dfrac { { d }^{ 2 }x }{ d{ t }^{ 2 } } +b\dfrac { dx }{ dt } +kx=0$
k = oscillating constant 
x = displacement of body from mean position 
b = constant depends on resistive medium 
v = velocity of object = $\dfrac{dx}{dt}$
m = mass of object .

Multiple choice physics floatation buoyancy fluid pressure option b: engineering physics

When a solid is completely immersed in a fluid, the apparent loss of weight of solid is _______ volume of fluid displaced 

  1. more than

  2. less than

  3. equal to

  4. cant say
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

From the principle of Archimedes, loss of weight is equal to the weight of the liquid displaced.

Multiple choice physics floatation buoyancy fluid pressure option b: engineering physics

When a body is fully immersed in a liquid the apparent loss in the weight of body is equal to :

  1. volume of liquid displaced by the body

  2. density of the liquid

  3. weight of liquid displaced by the body

  4. none of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

According to Archimedes principle, the weight of water displaced is equal to the weight of immersed part.For a solid floating in a liquid, its weight acting vertically down at its centre of gravity is equal to the weight of the liquid displaced by the immersed part of the solid acting vertically up at its centre of buoyancy. In the floating condition, the apparent weight and the apparent density of the solid are zero and the body is said to be weightless.

Multiple choice physics floatation buoyancy fluid pressure option b: engineering physics

State whether the weight of an iron sinker with cork combined in water will be more or less than that of the iron sinker alone in water. 

  1. Less

  2. More

  3. Same

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The weight of an iron sinker with cork combined in water will be less than that of the iron sinker alone in water.
This is because upthrust on cork due to water (when completely immersed) is greater than its weight.

Multiple choice physics option b: engineering physics buoyancy floatation fluid pressure

An incompressible liquid of density $\rho$ is contained in a vessel of uniform cross-sectional area $A$. If then atmospheric pressure is $p$, then the force acting on a horizontal plane of area a situated at a depth $d$ in liquid is given by

  1. $Ap+apgd$
  2. $\dfrac { p }{ A } +\dfrac { \rho gd }{ a }$
  3. $\dfrac { p+\rho gd }{ a }$
  4. $a\left( \rho\ gd+p \right)$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The pressure at depth d is P = p + rho*g*d. Force is pressure times area. Thus, F = P * a = (p + rho*g*d) * a = a(p + rho*g*d).