Physics WAEC

Simple Harmonic Motion

Gbogbo ọrọ náà

Welcome to the comprehensive course material on Simple Harmonic Motion in the realm of Physics. This topic delves into the fascinating interplay of matter, space, and time, unraveling the principles governing the oscillatory behavior of bodies in motion.

Simple Harmonic Motion (SHM) is a fundamental concept that underpins various natural phenomena, from the swinging of a pendulum to the vibrations of a spring. It is characterized by a periodic motion where the restoring force is directly proportional to the displacement of the object from its equilibrium position.

Understanding the Concept of SHM: In our exploration of SHM, we will delve into the essence of motion—how objects move in a repetitive manner around a central point. Through this, we aim to grasp the fundamental principles that govern the oscillations exhibited by bodies in harmonic motion.

Distinguishing Types of Motion: Among the myriad forms of motion, SHM stands out for its regular and predictable nature. By contrasting SHM with other types of motion like linear, rotational, and circular motion, we gain a deeper appreciation for its unique characteristics.

Calculating Speed and Acceleration: An integral part of our study involves computing the speed and acceleration of objects undergoing SHM. By analyzing the velocities and accelerations at different points in the oscillatory cycle, we can elucidate the dynamic nature of harmonic motion.

Determining Period, Frequency, and Amplitude: The period, frequency, and amplitude are crucial parameters that define the behavior of an oscillating body. By incorporating these measurements into our analysis, we can quantitatively describe the intricacies of SHM.

Exploring Energy in SHM: Energy considerations play a significant role in understanding SHM. By delving into the potential and kinetic energy transitions during oscillations, we unveil the energy dynamics at play within harmonic motion systems.

Unveiling Forced Vibration and Resonance: Beyond natural oscillations, we will delve into the phenomena of forced vibration and resonance. Through this exploration, we aim to elucidate how external forces can influence and amplify the oscillatory behavior of systems in SHM.

This course material serves as a comprehensive guide for unraveling the intricacies of Simple Harmonic Motion, offering a deep dive into the principles governing the oscillatory behavior of physical systems. By mastering the concepts elucidated herein, you will be equipped to analyze, calculate, and interpret the dynamic nature of harmonic motion with precision and insight.

Ebumnobi

  1. Define and calculate the speed and acceleration of bodies in Simple Harmonic Motion
  2. Discuss forced vibration and resonance phenomenon in the context of Simple Harmonic Motion
  3. Distinguish between different types of motion and identify Simple Harmonic Motion
  4. Calculate the period, frequency, and amplitude of Simple Harmonic Motion
  5. Understand the concept of Simple Harmonic Motion
  6. Analyze the energy involved in Simple Harmonic Motion

Akwụkwọ Ọmụmụ

Simple Harmonic Motion (SHM) is a type of periodic motion where an object moves back and forth over the same path, and each cycle takes the same amount of time. This type of motion is very common in nature and engineering and is seen in systems such as pendulums and springs. The restoring force in SHM is directly proportional to the displacement and acts in the direction opposite to that of displacement.

Nnyocha Ọmụmụ

Ekele diri gi maka imecha ihe karịrị na Simple Harmonic Motion. Ugbu a na ị na-enyochakwa isi echiche na echiche ndị dị mkpa, ọ bụ oge iji nwalee ihe ị ma. Ngwa a na-enye ụdị ajụjụ ọmụmụ dị iche iche emebere iji kwado nghọta gị wee nyere gị aka ịmata otú ị ghọtara ihe ndị a kụziri.

Ị ga-ahụ ngwakọta nke ụdị ajụjụ dị iche iche, gụnyere ajụjụ chọrọ ịhọrọ otu n’ime ọtụtụ azịza, ajụjụ chọrọ mkpirisi azịza, na ajụjụ ede ede. A na-arụpụta ajụjụ ọ bụla nke ọma iji nwalee akụkụ dị iche iche nke ihe ọmụma gị na nkà nke ịtụgharị uche.

Jiri akụkụ a nke nyocha ka ohere iji kụziere ihe ị matara banyere isiokwu ahụ ma chọpụta ebe ọ bụla ị nwere ike ịchọ ọmụmụ ihe ọzọ. Ekwela ka nsogbu ọ bụla ị na-eche ihu mee ka ị daa mba; kama, lee ha anya dị ka ohere maka ịzụlite onwe gị na imeziwanye.

  1. What is the main idea behind Simple Harmonic Motion? A. Objects moving in a straight line B. Objects moving in a circular path C. Objects moving in a periodic and oscillatory motion D. Objects moving with constant velocity Answer: C. Objects moving in a periodic and oscillatory motion
  2. Which of the following is not a characteristic of Simple Harmonic Motion? A. Periodic motion B. Linear motion C. Restoring force is directly proportional to displacement D. Motion repeats in equal intervals of time Answer: B. Linear motion
  3. In Simple Harmonic Motion, what is the relationship between displacement and acceleration? A. Directly proportional B. Inversely proportional C. No relationship D. Exponential Answer: A. Directly proportional
  4. What is the formula for calculating the period of a body in Simple Harmonic Motion? A. T = 2π / ω B. T = 2πω C. T = 1 / 2πω D. T = 2ω / π Answer: A. T = 2π / ω
  5. What physical quantity represents the maximum displacement from equilibrium in Simple Harmonic Motion? A. Frequency B. Period C. Amplitude D. Velocity Answer: C. Amplitude
  6. Which of the following expressions represents the kinetic energy of a body in Simple Harmonic Motion? A. 1/2kx^2 B. 1/2mv^2 C. 1/2kA^2 D. mgh Answer: B. 1/2mv^2
  7. In the context of Simple Harmonic Motion, what is resonance? A. The tendency of a system to oscillate at maximum amplitude at certain frequencies B. The complete absence of oscillation in a system C. The damping of oscillations over time D. The motion of a body at rest Answer: A. The tendency of a system to oscillate at maximum amplitude at certain frequencies

Ajụjụ Nnyocha

Nna, you dey wonder how past questions for this topic be? Here be some questions about Simple Harmonic Motion from previous years.

Ajụjụ 1 Ripọtì

A body is whirled in a horizontal circle at the rate of 800 revolutions per minute. Determine the angular velocity
Akọwa Nkọwa

To determine the angular velocity of a body whirled in a horizontal circle at a rate of 800 revolutions per minute (rpm), we need to convert this to the standard unit of angular velocity, which is radians per second (rad/s).


Here’s how you can calculate it:


  • First, understand that one complete revolution is equal to 2π radians.
  • The body completes 800 revolutions in one minute.

Now let's perform the conversion:


  • Convert the revolutions per minute to revolutions per second:
    • \( \frac{800 \text{ revolutions}}{1 \text{ minute}} \times \frac{1 \text{ minute}}{60 \text{ seconds}} = \frac{800}{60} \text{ revolutions per second} \), which simplifies to approximately \( 13.33 \text{ revolutions per second} \).
  • Convert revolutions to radians by multiplying by \(2π\) radians per revolution:
    • \( 13.33 \text{ revolutions per second} \times 2π \text{ radians per revolution} = 26.66π \text{ radians per second} \).

Rounding up the decimal to a consistent significant figure, the angular velocity is approximately 26.7π radians per second.


Ajụjụ 1 Ripọtì

You are provided with two retort stands, two-metre rules, pieces of thread and other necessary apparatus.

i. Set up the apparatus as illustrated above ensuring the strings are permanently 10cm from either end of the rule.

ii. Measure and record the length L = 80 cm of the two strings.

iii. Hold both ends of the rule and displace the rule slightly, then release so that it oscillates about a vertical axis through its centre.

iv. Determine and record the time t for 10 complete oscillations.

v. Determine the period T of oscillations.

vi. Evaluate log T and L.

vii. Repeat the procedure for four other values of L= 70 cm, 60 cm, 50 cm, and 40 cm

viii. Tabulate your readings.

ix. Plot a graph with log T on the vertical axis and log L on the horizontal axis.

x. Determine the slope, s, and the intercept, c on the vertical axis.

xi. State two precautions taken to ensure accurate results. 

(b)i. Define simple harmonic motion.

ii. Determine the value of L corresponding to t= 12 s from the graph in 1.

Akọwa Nkọwa

Bifilar pendulum: torsional oscillation of a suspended metre rule

The two threads of equal length \(L\) are fixed to the rigid horizontal support, each 10 cm from the ends of the metre rule, so that the rule hangs horizontally and can oscillate about the vertical axis through its centre.

figure
Bifilar pendulum: metre rule suspended by two threads of length L, each 10 cm from the ends, oscillating about the vertical axis through its centre.

For each length the period is obtained from the timing of ten complete oscillations:

\[ T = \frac{t}{10} \]

and \(\log T\) and \(\log L\) are then evaluated for each reading.

(viii) Table of readings

S/NL /cmt /s (10 osc.)T = t/10 /slog Tlog L
180.017.91.790.2531.903
270.016.71.670.2231.845
360.015.51.550.1901.778
450.014.11.410.1491.699
540.012.61.260.1001.602

(ix) Graph of log T against log L

graph
Straight-line graph of log T (vertical) against log L (horizontal); slope s = 0.51, intercept c = -0.71.

The points lie on a straight line, confirming that \( \log T = s\,\log L + c \).

(x) Slope and intercept

Taking two widely separated points on the line of best fit, \((1.602,\;0.100)\) and \((1.903,\;0.253)\):

\[ s = \frac{\Delta(\log T)}{\Delta(\log L)} = \frac{0.253 - 0.100}{1.903 - 1.602} = \frac{0.153}{0.301} = 0.51 \]

Extending the line back to \(\log L = 0\) (or using \( c = \log T - s\log L = 0.253 - 0.51\times1.903 \)) gives the vertical intercept:

\[ c = -0.71 \]

Hence \( \log T = 0.51\,\log L - 0.71 \), which corresponds to \( T \propto L^{1/2} \), the expected law for the bifilar pendulum.

(xi) Two precautions

  1. I avoided parallax error when reading the metre rule and when starting and stopping the stopwatch, by viewing each scale directly from the front.
  2. I ensured that the support was rigid and that the rule oscillated smoothly about a vertical axis through its centre with only a small angular displacement, counting the oscillations from a fixed reference mark.

(b)(i) Simple harmonic motion

Simple harmonic motion is the motion of a body whose acceleration is directly proportional to its displacement from a fixed point and is always directed towards that fixed point:

\[ a = -\omega^{2}x \]

(b)(ii) Value of L corresponding to t = 12 s

For \( t = 12\,\text{s} \):

\[ T = \frac{t}{10} = \frac{12}{10} = 1.2\,\text{s}, \qquad \log T = \log 1.2 = 0.079 \]

Reading from \( \log T = 0.079 \) on the vertical axis across to the line of best fit and down to the horizontal axis (or solving \( 0.079 = 0.51\log L - 0.71 \)):

\[ \log L = \frac{0.079 + 0.71}{0.51} = \frac{0.789}{0.51} = 1.56 \]\[ L = 10^{1.56} = 36\,\text{cm} \]

Therefore the length of the threads corresponding to \( t = 12\,\text{s} \) is \( L \approx 36\,\text{cm} \).


Ajụjụ 1 Ripọtì

A body executing simple harmonic motion has an angular speed of 2π radians. Its period of oscillation is (π 3.14).