Tag: shm as projection of circular motion

Questions Related to shm as projection of circular motion

Multiple choice physics simple harmonic motion representing shm with circular motion shm as projection of circular motion simple harmonic motion (shm) as a projection of uniform circular motion

A force acts on a $30$gm particle in such a way that the position of the particle as a function of time is given by $x=3t-4t^2+t^3$, where x is in metres and t is in seconds. The work done during the first $4$ second is?

  1. $2.88$J

  2. $450$mJ

  3. $490$mJ

  4. $530$mJ

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

$M=20gm=0.020kg$

$x=3t-4t²+t³m$
$v=dx/dt=3-8t+3t²m/s$
$a=dv/dt=-8+6tm/s²$
$Force=ma=0.120t-0.160N$
$Workdone=dW=Fdx=F\ast \frac { dx }{ dt } \ast dt=(0.120t-0.160)\ast (3-8t+3t²)dt=0.360t³-1.440t²+1.640t-0.480$
$W=0.090t⁴-0.490t³+0.82t²-0.480t=2.88J$

Multiple choice physics simple harmonic motion representing shm with circular motion shm as projection of circular motion simple harmonic motion (shm) as a projection of uniform circular motion

A wheel of radius $1$ meters rolls forward half a revolution on a horizontal ground. The magnitude of the displacement of the point of the wheel initially in contact with the ground is:

  1. $2 \pi$

  2. $\sqrt 2 \pi$

  3. $\sqrt {{\pi ^2} + 4} $

  4. $\pi$

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Let fro $A$ to $B$, where complete half a rotation.
we have,
$PQ=\alpha =$ half circumference $=\pi \ m$
and $P' Q=$ diameter $=2\ m$
so we have displacement of $P$
$x=|PP;|=\sqrt {PQ^2 +P; Q^2}$ (Pythagoras theorem)
$\Rightarrow \ x=\sqrt {\pi^2 +4}m$
Multiple choice physics simple harmonic motion representing shm with circular motion shm as projection of circular motion simple harmonic motion (shm) as a projection of uniform circular motion

Two SHMs are represented by the equations 
$y1=10sin(3\Omega t+\frac{\Omega }{4})$ and
$y2=5[sin3\Omega t+\sqrt{3}cos 3\Omega t]$. their amplitudes and in the ratio

  1. 1:2

  2. 2:1

  3. 1:3

  4. 1:1

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

Compare the given equations with,

$y=a\sin \omega t$

Where a is amplitude of wave

Here, a1 = 10

 a2 = 5

So the ratio is

$\dfrac{{{a} _{1}}}{{{a} _{2}}}=\dfrac{10}{5}=\dfrac{2}{1}$

Or $2:1$

Multiple choice physics simple harmonic motion representing shm with circular motion shm as projection of circular motion simple harmonic motion (shm) as a projection of uniform circular motion

A simple harmonic oscillator starts from extreme position and covers a displacement half of its amplitude in a time '$t$', the further time taken by it to reach mean position is

  1. $2t$

  2. $t$

  3. $ t/\sqrt{2} $

  4. $t/2$

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

$x=A cos(\omega t)$
Taking $t=0$ at extreme position.
$x=\dfrac{A}{2}$ is reached in time t
$\omega t=\dfrac{\pi }{3} ;\omega =\dfrac{\pi }{3t}$
$x=0$ is reached at $\omega t _{1}=\dfrac{\pi }{2}$
$t _{1}=\dfrac{\pi }{2\omega }=\dfrac{\pi \times 3t}{2\times\pi }=\dfrac{3t}{2}$
$t _{1}-t=\dfrac{t}{2}$

Multiple choice physics simple harmonic motion representing shm with circular motion shm as projection of circular motion simple harmonic motion (shm) as a projection of uniform circular motion

The circular motion of a particle whose speed is constant is

  1. Periodic but not simple harmonic

  2. Simple harmonic but not periodic

  3. Periodic and simple harmonic

  4. Neither periodic not simple harmonic

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Uniform circular motion is a periodic motion but not simple harmonic

The correct option is (a)

Multiple choice physics simple harmonic motion representing shm with circular motion shm as projection of circular motion simple harmonic motion (shm) as a projection of uniform circular motion

The particle executes SHM on a straight line. At two positions its velocity $u$ and $v$ while acceleration, $\alpha$ and $\beta$ respectively $[\beta > \alpha >0]$, the distance between the two positions will be:-

  1. $\dfrac{u^2+v^2}{\alpha+\beta}$

  2. $-\dfrac{u^2-v^2}{\alpha+\beta}$

  3. $\dfrac{u^2-v^2}{\alpha-\beta}$

  4. $\dfrac{u^2+v^2}{\beta-\alpha}$

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

We know that velocity is related as,

$u=\omega \sqrt{A^2-X _1^2}$
$v=\omega\sqrt{A^2-X _2^2}$
Acceleration is related as,
$\alpha=-\omega^2X _1^2$
$\beta=-\omega^2X _2^2$
$\dfrac{u^2-v^2}{u^2}=-(X _1^2-X _2^2)$
$=-(X _1+X _2)(X _1-X _2)$
$=\dfrac{\alpha+\beta}{u^2}(X _1-X _2)$
$X _1-X _2=-\dfrac{u^2-v^2}{\alpha+\beta}$

Multiple choice physics simple harmonic motion representing shm with circular motion shm as projection of circular motion simple harmonic motion (shm) as a projection of uniform circular motion

A ball is projected from the ground at angle 0 with the horizontal. After 1 sec it is moving at angle ${ 45 }^{ \circ  }$ with the horizontal and after 2s it is moving horizontally. What is the velocity of projection of the ball ? (Take $g=10\quad { ms }^{ -2 }$)

  1. $10\sqrt { { 3ms }^{ -1 } } $

  2. $20\sqrt { { 3ms }^{ -1 } } $

  3. $10\sqrt { { 5ms }^{ -1 } } $

  4. $20\sqrt { { 2ms }^{ -1 } } $

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using kinematic equations for projectile motion: vx = v*cos(theta), vy = v*sin(theta) - gt. At t=1, vy/vx = tan(45) = 1. At t=2, vy = 0, so v*sin(theta) = 2g = 20. Solving these gives the initial velocity.

Multiple choice physics simple harmonic motion representing shm with circular motion shm as projection of circular motion simple harmonic motion (shm) as a projection of uniform circular motion

To understand Simple Harmonic Motion as analogous to circular motion,

  1. we project the circular motion of the particle along any radius.

  2. we project the circulation motion of the particle along a chord.

  3. we project the circulation motion of the particle along the diameter.

  4. None of these.

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The circular motion can be resolved into a S.H.M. In this process we project circular motion of particle along diameter the projection of particle performs S.H.M. with centres as mean positions.

Multiple choice physics simple harmonic motion representing shm with circular motion shm as projection of circular motion simple harmonic motion (shm) as a projection of uniform circular motion

The actual distance moved along the circle will be                   the distance moved by the projection on the diameter.

  1. less than

  2. equal to

  3. greater than

  4. None of these

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let the radius of the circle be $R$.

Thus distance moved along the circle  $D = \pi R = 3.14 R$
Projection of this distance along the diameter is equal to the diameter of the circle i.e.  $2R$
Thus actual distance moved along the circle will be greater than the distance moved by the projection on the diameter.