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801.

A particle executing SHM has a frequency of 10 Hz when it crosses its equilibrium position with a velocity of `2pi m//s`. Then the amplitude of vibration isA. 0.1 mB. 0.2 mC. 0.4 mD. 1 m

Answer» Correct Answer - A
`v_(m)=Aomega`
`therefore A=(v_(m))/(2pin)=(2pi)/(2pixx10)=0.1m`
802.

A simple harmonic motion is represented by x(t) = 10 sin(20t + 0.5)Find its amplitude, frequency and initial phase.

Answer»

Comparing the given equation with standard equation of S.H.M.

x(t) = a sin(ωt + ϕo)

(i) Amplitude, a = 10 m

(ii) Angular frequency, 

ω = 20 rad s-1

(iii) Frequency is given by 

v = \(\frac{ω}{2\pi}\) = 3.18 Hz

(iv) Initial phase, ϕo = 0.5 rad.

803.

A particle executes simple harmonic motion with a period of `16s`. At time `t=2s`, the particle crosses the mean position while at `t=4s`, its velocity is `4ms^-1` amplitude of motion in metre isA. `sqrt(2) pi`B. `16 sqrt(2) pi`C. `24 sqrt(2) pi`D. `32 sqrt(2)//pi`

Answer» Correct Answer - D
For simple harmonic motion, y = a sin `omega`t
`therefore" "y = a sin ((2pi)/(T))t" "("at t"=2s)`
`y_(1)=a sin [((2pi)/(16))xx2]=a sin((pi)/(4))=(a)/(sqrt(2))" "...(i)`
At t = 4 s or after 2 s from mean position.
`y_(1)=(a)/(sqrt(2))"and velocity"=4 ms^(-1)`
`therefore` Velocity `= omega sqrt(a^(2)-y_(1)^(2))`
or `4 = ((2pi)/(16))sqrt(a^(2)-(a^(2))/(2))" "["From Eq. (i)"]`
or `4 = (pi)/(8) xx (a)/(sqrt(2))or a = (32 sqrt(2))/(pi)m`
804.

Time period of a particle executing SHM is 16s.At time `t = 2s`, it crosses the mean position . Its amplitude of motion is `( 32sqrt(2))/(pi) m`. Its velocity at `t = 4s` isA. `1 ms^(-1)`B. ` 2ms^(-1)`C. ` 4ms^(-1)`D. `8 ms^(-1)`

Answer» Correct Answer - 3
805.

The equation of motion of a particle started at `t=0` is given by `x=5sin(20t+pi//3)` where x is in centimeter and t in second. When does particle (a) first come to rest (b) first have zero acceleration (c) first have maximum speed?A. `(pi)/(90)sec`B. `(pi)/(120)sec`C. `(pi)/(60)sec`D. `(pi)/(30)sec`

Answer» Correct Answer - D
`a = (d^(2)y)/(dt^(2)) =0` at mean position, particle is initially moving towards positive exterme.
806.

The potential energy of a particle oscillating on x-axis is given as `U +20 +(x-2)^(2)`. The mean position is atA. `x =2m`B. `x =1m`C. `x =3m`D. `x =4m`

Answer» Correct Answer - A
`U` is minimum at mean position so mean position is at `x = 2m`
807.

A particle executes simple harmonic motion with a period of `16s`. At time `t=2s`, the particle crosses the mean position while at `t=4s`, its velocity is `4ms^-1` amplitude of motion in metre isA. `sqrt(2)pi`B. `16sqrt(2)pi`C. `32sqrt(2)//pi`D. `4//pi`

Answer» Correct Answer - C
`y_(1) = A sin ((2pi)/(T)xxt), V = omega sqrt(A^(2) - y_(1)^(2))`
808.

A simple pendulum of length `l` is connected to the ceiling of a vehicle that is moving down along a smooth inclined plane `4` in `5`. Then its period of oscillation isA. `2pi sqrt((5l)/(4g))`B. `2pisqrt((4l)/(5g))`C. `2pisqrt((5l)/(3g))`D. `2pi sqrt((3l)/(5g))`

Answer» Correct Answer - C
`T = 2pi sqrt((l)/(g cos theta))`
809.

A particle starts SHM from mean position O executing SHM A and B are the two point at which its velocity is zero . It passes through a certain point P at time `t_(1) = 0.5 and t_(2) = 1.5 s` with a speed of `3 m//s`. i. The maximum speed ....... ii. ratio `AP//PB` .....A. `3m//s`B. `3sqrt(2)m//s`C. `3sqrt(3)m//s`D. `6m//s`

Answer» Correct Answer - B
`T = 2sec, v = omega sqrt(A^(2) -x^(2)), v = 3m//sec` at `x = (A)/(sqrt(2)), v_(max) = A omega`
810.

The relation between acceleration and displacement of four particles are given below. The particle undergoing SHM is:A. `a_(x) = +2x`B. `a_(x) =+2x^(2)`C. `a_(x) =- 2x^(2)`D. `a_(x)= -2x`

Answer» Correct Answer - D
In option `(d)a_(x) = - 2x` or `a alpha -x`, the acceleration of the particle is proportional to negative of displaement. Hence it represnts `S.H.M`.
811.

A block is kept on a rough horizontal plank. The coefficient of friction between block and plank is `1//2`. Plank is undergoing `SHM` is angular frequency `10 rad//s`. Find the maximum amplitude of plank in which the block does slip over plank `(g = 10 m//s^(2))`.

Answer» Maximum acceleration in `SHM` is `a_(max) = •^(2)A` this will be provided to the block by friction. Hence,
`a_(max) = •g or •^(2)A = •g`
or `A = (•g)/(•^(2)) = (((1)/(2))(10))/((10)^(2)) =0.05m = 5cm`
812.

Give some practical examples of S. H. M?

Answer»

Some practical examples of S. H. M. are :- 

1) Motion of piston in a gas – filled cylinder. 

2) Atoms vibrating in a crystal lattice. 

3) Motion of helical spring.

813.

In 20 s, two simple pendulums, P and Q, complete 9 and 7 oscillations, respectively, on the Earth. On the Moon, where the acceleration due to gravity is \(\frac16\)th that on the Earth, their periods are in the ratio (A) 8 : 1 (B) 9 : 7 (C) 7 : 9 (D) 3 : 14.

Answer»

Correct option is (C) 7 : 9

814.

A seconds pendulum is suspended in an elevator moving with a constant speed in the downward direction. The periodic time (T) of that pendulum is (A) less than two seconds (B) equal to two seconds (C) greater than two seconds (D) very much greater than two seconds.

Answer»

(B) equal to two seconds

815.

If T is the time period of a simple pendulum in an elevator at rest, its time period in a freely falling elevator will be(A) \(\frac{T}{\sqrt2}\)(B) √2T (C) 2T (D) infinite.

Answer»

Correct option is (D) infinite.

816.

STATEMENT-1`:` Time periodof oscillation of a simple pendulum mounted in a cabin that is freely falling is zero and STATEMENT -2 `,` In the cabin falling freely under gravity the pendulum is in state of weightlessness.

Answer» Correct Answer - 4
817.

Time period of a simple pendulum in a freely falling lift will beA. FiniteB. InifiniteC. ZeroD. All of these

Answer» Correct Answer - 2
818.

The displacement of a particle making S.H.M. is given by `x=6cos(100t+(pi)/(4))m` then the frequency isA. `1.592 Hz`B. `15.92 Hz`C. `159.2 Hz`D. `1592 Hz`

Answer» Correct Answer - B
`x=6cos(100t+(pi)/(4))`
`omega=100`
`2pin=100`
`n=(100)/(2pi)=(50)/(pi)=15.92Hz`.
819.

A particle oscillating under a force `vecF=-kvecx-bvecv` is a (k and b are constants)A. Linear oscillationB. Forces oscillationsC. Damped oscilationD. SHM

Answer» Correct Answer - 3
820.

The displacement of a particle of mass 100 g executing SHm is given by the equation y = 0.2 cos `(100t+(pi)/(4))` meter. Its total energy isA. 1 JB. 10 JC. 2 JD. 20 J

Answer» Correct Answer - D
`E=(1)/(2)momega^(2)A^(2)=(1)/(2)xx0.1xx100^(2)xx(0.2)^(2)`
`=20J`
821.

Displacement of a particle executing SHM s `x= 10 ( cos pi t + sin pi t)`. Its maximum speed isA. `5 pi m//s`B. ` 10 pi m//s`C. ` 10 sqrt(2) pi m//s`D. ` 5 sqrt(2 ) pi m//s`

Answer» Correct Answer - 3
822.

Displacement time equation of a particle executing `SHM` is, `x = 10 sin ((pi)/(3)t+(pi)/(6))cm`. The distance covered by particle in `3s` isA. `5cm`B. `20cm`C. `10cm`D. `15cm`

Answer» Correct Answer - B
`X = A sin (omegat +ph), T = (2pi)/(omega)`
823.

Displacement of a particle executing SHM s `x= 10 ( cos pi t + sin pi t)`. Its maximum speed isA. 10 cmB. 20 cmC. `5 sqrt(2)` cmD. 50 cm

Answer» Correct Answer - A
Here, `x = 5 sqrt(2) (sin 2 pi t + cos 2 pi t)`
`rArr" "x = 5 sqrt(2) sin 2 pi t + 5 sqrt(2) cos 2 pi t" "...(i)`
The standard equation of simple harmonic motion is given by
`x = A_(1) sin omega t + A_(2) cos omega t" "...(ii)`
Now, comparing Eqs. (i) and (ii), we obtain
`A_(1)=5 sqrt(2) and A_(2)=5 sqrt(2)`
So, the resultant amplitude of the motion
`A = sqrt(A_(1)^(2)+A_(2)^(2))=sqrt((5 sqrt(2))^(2)+(5 sqrt(2))^(2))= 10` cm
824.

Time period of a simple pendulum will be double, if weA. decrease the length 2 timesB. decrease the length 4 timesC. increase the length 2 timesD. increase the length 4 times

Answer» Correct Answer - D
The formula for time period is, `T = 2pi sqrt((l)/(g)) prop sqrt(l)`
If the length is increased by four times, then time period will be doubled.
825.

The velocity of a particle performing simple harmonic motion, when it passes through its mean position iA. infinityB. zeroC. minimumD. maximum

Answer» Correct Answer - D
The relation for velocity of a particle executing SHM is given by, `v = omega sqrt(A^(2) - y^(2))`. Hence, at mean position y = 0.
The velocity is maximum. `V_(max) = A omega` (where, A is amplitude)
826.

Two springs, of spring constants `k_(1)` and `K_(2)`, have equal highest velocities, when executing SHM. Then, the ratio of their amplitudes (given their masses are in the ratio `1:2`) will beA. `((k_(2))/(k_(1)))^(1//2)`B. `((k_(1))/(k_(2)))^(1//2)`C. `(k_(1))/(k_(2))`D. `k_(1)k_(2)`

Answer» Correct Answer - A
The angular frequency of spring is given by
`omega = sqrt((k)/(m)) prop sqrt(k)`
For equal maximum velocities, we have
`A_(1)omega_(1) = A_(2)omega_(2)`
or `(A_(1))/(A_(2))=(omega_(2))/(omega_(1))=sqrt((k_(2))/(k_(1)))=((k_(2))/(k_(1)))^((1)/(2))" "(because m = m_(1) = m_(2))`
827.

Two springs of constants `k_1` and `k_2` have equal maximum velocities, when executing simple harmonic motion. The ratio of their amplitudes (masses are equal) will beA. `(k_(1))/(k_(2))`B. `(k_(2))/(k_(1))`C. `((k_(1))/(k_(2)))^(1//2)`D. `((k_(2))/(k_(1)))^(1//2)`

Answer» Correct Answer - D
`v_(1)=v_(2)`
`A_(1)omega_(1)=A_(2)omega_(2)`
`(A_(1))/(A_(2))=(omega_(2))/(omega_(1))=(T_(1))/(T_(2))=sqrt((k_(2))/(k_(1)))`
828.

A spring of force constant `600 Nm^(-1)` is mounted on a horizontal table. A mass of 1.5 kg is attached to the free end of the spring,pulled sideways to a distance of 2 cm and released . The speed of the mass when the spring is compressed by 1 cm isA. `0.175 ms^(-1)`B. ` 0. 35 ms^(-1)`C. ` 0.7 ms^(-1)`D. ` 1.4 ms^(-1)`

Answer» Correct Answer - 2
829.

A spring of force constant `600 Nm^(-1)` is mounted on a horizontal table. A mass of 1.5 kg is attached to the free end of the spring, pulled sideways to a distance of 2 cm and released .P.E. of the mass when it momentarily comes to rest and total energy areA. `0.12 J , 0`B. ` 0,0.12 J`C. `0,0`D. ` 0.12 J , 0.12J`

Answer» Correct Answer - 4
830.

If the earth were a homogeneous sphere of radius R and a straight hole bored in it through its centre, show that a body dropped into the hole will execute SHM and find its time period.

Answer» Correct Answer - 5077.6s
831.

If a hole is bored along the diameter of the earth and a stone is dropped into holeA. reaches the centre of the earth and stopsB. reaches the other side of the earth and stopsC. executes simple harmonic motion about the centre of the earthD. reaches the other side of the earth and escapes into space

Answer» Correct Answer - C
832.

The total energy of a simple pendulum is x. When the displacement is half of amplitude,its KE will beA. `(x)/(2)`B. `(x)/(4)`C. `(3x)/(4)`D. `x`

Answer» Correct Answer - 3
833.

Two identical springs have the same force constant of `147Nm^(-1)`. What elongation will be produced in each spring in each case shown in figure? `g=9.8ms^(-2)`. A. `(1)/(6)m,(2)/(3) m, (1)/(3)m`B. `(1)/(3)m,(1)/(3)m,(1)/(3)m`C. `(2)/(3)m,(1)/(3)m,(1)/(6)m`D. `(1)/(3)m,(2)/(3)m,(2)/(3)m`

Answer» Correct Answer - 4
834.

A body of mass m is situated in a potential field `U(x)=U_(0)(1-cosalphax)` when `U_(0)` and `alpha` are constant. Find the time period of small oscialltions.A. `2pisqrt((m)/(U_(0)alpha))`B. `2pisqrt((m)/(U_(0)alpha^(2)))`C. `2pisqrt((m)/(2U_(0)alpha))`D. `2pisqrt((2m)/(U_(0)alpha^(2)))`

Answer» Correct Answer - B
Given: `U=U_(0)(1-cosalphax)`
`becauseF=-(dU)/(dx)`
`thereforeF=-(d)/(dx)[U_(0)(1-cosalphax)]=-U_(0)alphasinalphax`
As `alphax` is small, so `sinalphax ~ alphax`
`thereforeF=-U_(0)alpha^(2)x` . .. (i)
`Fpropx and -ve` shows that F is directed towards the mean position, hence the body executes SHM.
For SHM, `F=-kx`
Comparing (i) and (ii), we get, `k=U_(0)alpha^(2)`
Time period of oscillation,
`T=2pisqrt((m)/(k))=2pisqrt((m)/(U_(0)alpha^(2)))`
835.

A mass m is vertically suspended from a spring of negligible mass, the system oscillates with a frequency n. what will be the frequency of the system, if a mass `4m` is suspended from the same spring?A. `(n)/(4)`B. `4n`C. `(n)/(2)`D. `2n`

Answer» Correct Answer - C
836.

The frequency of oscillation of amass m suspended by a spring is `v_(1)`. If length of spring is cut to one third then the same mass oscillations with frequency `v_(2)`. ThenA. `v_(2) = 3v_(1)`B. `3v_(2)=v_(1)`C. `v_(2)= sqrt(3)v_(1)`D. `sqrt(3)v_(2)=v_(1)`

Answer» Correct Answer - 4
837.

If a simple pendulum oscillates with an amplitude of 50 mm and time period of 2 sec, then its maximum velocity isA. `0.10 m//s`B. `0.16 m//s`C. `0.25 m//s`D. `0.5 m//s`

Answer» Correct Answer - B
`v_(m)=Aomega`
`=50xx10^(-3)xx(2pi)/(2)`
`=50xx10^(-3)xx3.14-15.700xx10^(-2)`
`=0.157m//s`
`~~0.16m//s`
838.

When a dampled harmonic oscillator completes 100 oscillations, its amplitude is reduced to `(1)/(3)` of its initial value. When will be its amplitude when it completes 200 oscillations?A. `(1)/(5)`B. `(2)/(3)`C. `(1)/(6)`D. `(1)/(9)`

Answer» Correct Answer - D
839.

Mass suspended to a spring is pulled down by 2.5 cm and let go. The mass oscillates with an amplitude ofA. 2.5 cmB. 5 cmC. 7.5 cmD. 10 cm

Answer» Correct Answer - 1
840.

The frequency of oscillations of a mass m suspended by spring of `v_(1)`. If the length of the spring is cut to one-third, the same mass oscillates with frequency `v_(2)`. Determing the value of `v_(2)//v_(1)`A. `2`B. `sqrt(2)`C. `4`D. `sqrt(3)`

Answer» Correct Answer - B
The frequency of oscillations of mass m and force constant k is, `upsilon_(1)=(1)/(2pi)sqrt((k)/(m))`
When the spring is cut to one-half of its length, its force constant is doubled (2k).
then frequency of oscillation of mass m will be
`upsilon_(2)=(1)/(2pi)sqrt((2k)/(m))" "therefore(upsilon_(2))/(upsilon_(1))=sqrt(2)`
841.

A block of mass `M` suspended from a spring oscillates with time period `T`. If spring is cut in to two equal parts and same mass `M` is suspended from one part, new period os oscillation isA. `(T)/(sqrt(2))`B. `sqrt(2)T`C. `T`D. `2T`

Answer» Correct Answer - A
`T = 2pi sqrt((m)/(K))`
842.

A spring-and-block oscillator with an ideal spring of force constant 180 N/m oscillates with a frequency of 6 Hz. The mass of the block is, approximately,(A) \(\frac18\) kg (B) \(\frac14\) kg (C) 4 kg (D) 8 kg.

Answer»

Correct option is (A) \(\frac18\) kg 

843.

What is meant by periodic and non-periodic motion? Give any two examples, for each motion.

Answer»

Periodic motion: Any motion which repeats itself in a fixed time interval is known as periodic motion. 

Examples: Hands in pendulum clock, swing of a cradle. 

Non-Periodic motion: Any motion which does not repeat itself after a regular interval of time is known as non-periodic motion. 

Example: Occurrence of Earth quake, eruption of volcano.

844.

What is meant by Oscillatory motion?

Answer»

When an object or a particle moves back and forth repeatedly for some duration of time, its – motion is said to be oscillatory (or vibratory).

845.

When a particle is performing linear `SHM` its `KE` is two times its `pE` at a position `A` and its `PE` is two times its `KE` at another position `B`. Find ratio of `KE_(A)` to `KE_(B)`

Answer» `TE_(A) = KE_(A) +PE_(A)`
But `KE_(A) = 2PE_(A)`,
`TE_(A) = KE_(A) +(1)/(2)KE_(A) = (3)/(2) KE_(A)`.
Similarly, `TE_(B) = KE_(B) +PE_(B)`.
But `PE_(B) = 2KE_(B)`
`TE_(B) = kE_(B) +2KE_(B) = 3KE_(B)`.
By the principle of conservation of energy
`TE_(A) = TE_(B), (3)/(2) KE_(A) = 3KE_(B)`
`(KE_(A))/(KE_(B)) = (2)/(1)`
846.

If the KE of a particle performing a SHM of amplitude A is `(3)/(4)` of its total energy, then the value of its displacement isA. `x=pm(A)/(2)`B. `x=pm(A)/(4)`C. `x=pm(sqrt(3A))/(2)`D. `x=pm(A)/(sqrt(2))`

Answer» Correct Answer - A
`K.E.=(3)/(4)T.E.`
`(1)/(2)momega^(2)(A^(2)-x^(2))=(3)/(4)xx(1)/(2)momega^(2)A^(2)`
`A^(2)-x^(2)=(3)/(4)A^(2)`
`A^(2)-(3)/(4)A^(2)=x^(2)`
`(A^(2))/(4)=x^(2)`
`therefore x=(A)/(2)`
847.

Variation of acceleration a of a particle executing HSM with displacement x isA. B. C. D.

Answer» Correct Answer - 3
848.

A horizontal spring-and-block system consists of a block of mass 1 kg, resting on a frictionless surface, and an ideal spring. A force of 10 N is required to compress the spring by 10 cm. The spring constant of the spring is (A) 100 N.m-1 (B) 10N.m-1  (C) N.m-1  (D) 0.1 N.m-1 

Answer»

Correct option is (C) N.m-1  

849.

At what displacement is the `KE` of a particle performing `SHM` of amplitude `10cm` is three times its `PE`?A. `2.5cm`B. `5cm`C. `7.5 cm`D. `10cm`

Answer» Correct Answer - B
`K.E. = 3.P.E.`
`P.E. = (1)/(2) m omega^(2)x^(2), K.E. =(1)/(2) m omega^(2) (A^(2)-x^(2))`
850.

The `KE` and `PE` , at is a particle executing `SHM` with amplitude `A` will be equal when its displacement isA. `A sqrt(2)`B. `(A)/(sqrt(2))`C. ` (A)/(2)`D. `A`

Answer» Correct Answer - 2