PH8151 ENGINEERING PHYSICS (UNIT 2)

19 flashcards · Physics · by Sathyaraj Duraisamy

  1. The periodic time of a body executing simple harmonic motion is 4s. After how many intervals from time t=0, its displacement will be half of its amplitude?

    t=1t/12=4/12=1/3 s.

  2. A spring (spring constant = k) is cut into 4 equal parts and two parts are connected in parallel. What is the effective spring constant?

    Spring constant of each one-fourth part = 4k When two parts are connected in parallel, kp=4k+4k=8k.

  3. Statement: Water in a U-tube executes simple harmonic motion. The time period for mercury filled up to the same height in the U-tube be greater than that in case of water. Reason: The amplitude of an oscillating pendulum goes on increasing. a) Both statement and reason are true and the reason is the correct explanation of the statement b) Both statement and reason are true but the reason is not the correct explanation of the statement c) Statement is true, but the reason is false d) Statement a…

    Both the statement and reason are false. Period of oscillation of a liquid in a U-tube is independent of the density of the liquid. The amplitude is the oscillating pendulum decreases due to air friction.

  4. If a spring of mass 30kg has a spring constant of 15N/m, then its time period is ___________

    : T=2π√(m/k) T=2π√(30/15)=2π√2 s.

  5. For a particle executing simple harmonic motion, which of the following statements is not correct?

    At the equilibrium position, the velocity of a particle in simple harmonic motion is maximum and consequently its acceleration is minimum.

  6. The ratio of frequencies of two pendulums is 2:3 then their lengths are in ratio ___________

    v1/v2 = √(l2/l1) l1/l2 = ((v2)2)/((v1)2)=9/4.

  7. Two simple motions are represented by, y1=5(sin2πt+√3 cos2πt) and y2= 5sin (2πt+π/4) The ratio of the amplitude of two simple harmonic motions is?

    y1=5×2(sin2πtcos(π/3)+sin⁡(π/3)cos2πt) y1=10sin⁡(2πt+(π/3):y2=5sin⁡(2πt+(π/4)) i.e., A1/A2=10/5=2:1.

  8. A body executes simple harmonic motion. The potential energy, the kinetic energy and total energy are measured as a function of displacement x. Which of the following statements is true?

    The kinetic energy of a simple harmonic oscillator is maximum when x = 0.

  9. The total energy of a particle executing simple harmonic motion is ___________

    E=2π2mv2A2 Clearly, the total energy is independent of displacement x.

  10. The bob of the pendulum moves faster at the lowest position for a larger amplitude.

    We know that the velocity of a simple pendulum is maximum at the lowest position and is given by vmax=ωA. That is for larges amplitude, the bob of the pendulum would move faster.

  11. The disc of a siren containing 60holes rotates at a constant speed of 360rpm. The emitted sound is in unison with a tuning fork of frequency.

    Frequency of revolution of disc=360rpm=360/60rps=60rps Frequency of emitted sound = 6×No.of holes =6×60=360Hz.

  12. The quantity which does not change, when sound enters from one medium to another __________

    Frequency remains unchanged when sound travels from one medium to another.

  13. The equation of a simple harmonic wave is given by y=5sin⁡(π/2) (100t-x). Where x and y are in metre and time is in second. The period of the wave in second will be _________

    y=5sin(π/2) (100t-x) y=Asin(ωt-kx) ω=2π/T=π/2×100 T=2/50=0.04s.

  14. If wave y=Acos(ωt+kx) Is moving along x-axis, the shapes of a pulse at t=0 and t=2s.

    The shapes of y-x graph remains the same at t=0 and t=2s.

  15. y1=4sin⁡(ωt+kx), y2=-4cos⁡(ωt+kx), the phase difference is __________

    y1=4sin(ωt+kx), y2=-4cos(ωt+kx)=-4sin(ωt+kx+3π/2):∆φ=3π/2

  16. A wave equation is y=0.1sin[100πt-kx] and wave velocity is 100m/s, its number is equal to __________

    y=0.1sin⁡[100πt-kx] y=Asin(ωt-kx) ω=100π Wave number=ω/v=100π/100=π/m.

  17. A particle on the trough of a wave at any instant will come to the mean position after a time (T=time period).

    Time taken by a particle to move from trough to the mean position=T/4.

  18. A string is tied on a sonometer, second end is hanging downward through a pulley with tension T. The velocity of the transverse wave produced is proportional to __________

    v=√(T/m) v∝√T.

  19. The fundamental frequency of a sonometer wire is n. If the tension is made 3 times and length and diameter are also increased 3 times, the new frequency will be __________

    n=1/LD×√(T/πρ) n‘=1/(3L×3D)×√(3T/πρ)=√3/9×n=1/(3√3) n.