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SIMPLE HARMONIC MOTION
▢ Periodic Motion:
❖ Definition: Motion in which position repeats after a fixed interval of time
❖ Types:
- •Rectilinear periodic motion
- •Closed curvilinear periodic motion
- •Open curvilinear periodic motion
❖ Examples:
Table 1: Periodic Motion Examples
Motion | Period |
|---|---|
Revolution of Earth around Sun | 1 year |
Rotation of Earth about polar axis | 24 hours |
▢ Oscillatory / Vibratory Motion:
❖ Definition: To-and-fro or back-and-forth repeated motion about a fixed mean position
❖ Mean Position: Fixed equilibrium position
❖ Extreme Positions: Two fixed limits of oscillation
❖ Relation:
- •Oscillatory motion is constrained periodic motion
- •All oscillatory motions are periodic
- •All periodic motions are not oscillatory
▢ Simple Harmonic Motion:
❖ Definition: Periodic to-and-fro motion about mean position under restoring force/acceleration directed towards mean position and proportional to displacement
❖ Condition:
Table 1: Necessary Condition for SHM
Quantity | Relation |
|---|---|
Acceleration | |
Force | |
Restoring force | |
Negative sign | Force always directed towards mean position |
❖ Important Relation: All SHM are periodic but all periodic motions are not SHM
▢ Types of SHM:
Table 1: Linear vs Angular SHM
Type | Definition | Condition | Differential equation |
|---|---|---|---|
Linear SHM | Oscillatory motion in straight line about mean position | ||
Angular SHM | Oscillatory motion about an axis |
❖ Angular Frequency:
Table 1: Frequency Relations
Quantity | Formula |
|---|---|
Angular frequency | |
Frequency | |
Time period | Independent of amplitude |
▢ Equations of SHM:
Table 1: SHM Formulae
Quantity | Formula |
|---|---|
Displacement | |
Velocity | |
Acceleration | |
Force | |
Momentum | |
Kinetic energy | |
Potential energy | |
Total energy |
❖ At Mean and Extreme Positions:
Table 1: Values at Mean and Extreme Position
Quantity | Mean position | Extreme position |
|---|---|---|
Displacement | ||
Velocity | ||
Acceleration | ||
Force | ||
Kinetic energy | Maximum | 0 |
Potential energy | 0 | Maximum |
Total energy | Constant | Constant |
▢ Graphs of SHM:
Table 1: SHM Graphs
Graph | Nature |
|---|---|
Displacement-time | Sine curve |
Velocity-time | Sine/cosine curve |
Acceleration-time | Sine curve |
Force-time | Sine curve |
Momentum-time | Sine curve |
Velocity-displacement | Ellipse |
Displacement-acceleration | Straight line with negative slope |
Displacement-force | Straight line with negative slope |
K.E.-displacement | Parabola |
P.E.-displacement | Parabola |
Total energy-displacement | Straight line parallel to X-axis |
❖ Velocity-Displacement Equation:
❖ Acceleration-Displacement Slope:
❖ Force-Displacement:
▢ Simple Pendulum:
❖ Restoring Force:
❖ Acceleration:
❖ Time Period:
❖ Properties:
- Time period independent of mass of bob
- Time period independent of shape/material of bob
- Time period independent of small amplitude
◈ _*type: bullet
❖ General Formula:
❖ Time Period in Various Cases:
Table 1: Simple Pendulum Special Cases
Case | Time period |
|---|---|
Normal condition | |
Lift moving with constant velocity | |
Length comparable to Earth radius | |
❖ Height and Depth Corrections:
Table 1: Clock Error Formulae
Condition | Change in time period | Loss in time per day |
|---|---|---|
Temperature change | Summer: clock slow; winter: clock fast |
▢ Spring Oscillation:
❖ Restoring Force:
❖ Acceleration:
❖ Time Period:
❖ Properties:
- •
- •Time period unchanged on Moon / height / depth if same mass-spring system
- •Spring system needs elasticity and inertia
❖ Spring Combination:
Table 1: Series vs Parallel Springs
Feature | Series | Parallel |
|---|---|---|
Force | ||
Extension | ||
Equivalent spring constant |
❖ Spring Constant:
◉ _*table:
❖ Special Spring Cases:
Table 1: Spring Oscillation Special Cases
Case | Time period |
|---|---|
❖ Spring Cut in Ratio:
Table 1: Spring Cut into m:n Ratio
Part | Spring constant |
|---|---|
▢ Motion Through Earth's Centre:
❖ Condition: Body moving inside a tunnel drilled through centre of Earth
❖ Restoring Force:
❖ Acceleration:
❖ _*table:
▢ Oscillation of Liquid in U-tube:
❖ Symbols:
- •
- •
- •
- •
❖ Restoring Force:
❖ Acceleration:
❖ Time Period:
❖ Independent Of:
- •Area of cross-section of U-tube
- •Density of liquid
❖ Depends On:
- •Length of liquid column
- •Acceleration due to gravity
▢ Oscillation of Block in Liquid:
❖ Symbols:
Table 1: Symbols
Symbol | Meaning |
|---|---|
Density of block | |
Density of liquid | |
Cross-sectional area of block | |
Mass of block | |
Vertical height of block inside liquid at equilibrium |
❖ Restoring Force:
❖ Time Period:
Table 1: Block in Liquid
Condition | Formula |
|---|---|
General | |
Using block density and height | |
▢ Time Shortcuts in SHM:
Table 1: Time Taken in SHM
Path | Time |
|---|---|
Extreme to mean | |
Mean to extreme | |
Complete oscillation displacement | 0 |
Complete oscillation distance |
▢ Phase Relations:
Table 1: Phase Difference in SHM
Quantities | Phase difference |
|---|---|
Displacement and velocity | |
Velocity and acceleration | |
Displacement and acceleration | |
Acceleration and force | 0 |
K.E. and P.E. |
❖ Initial Phase:
Table 1: Starting Point and Phase
Starting point | Equation | |
|---|---|---|
Mean position | 0° | |
Extreme position | 90° |
▢ Energy Frequency:
Table 1: Energy Oscillation
Quantity | Frequency / Period |
|---|---|
SHM frequency | |
K.E. frequency | |
P.E. frequency | |
K.E. and P.E. time period | |
Total energy frequency | 0 |
Total energy | Same at all positions |
▢ Undamped and Damped Oscillations:
Table 1: Oscillation Types
Type | Meaning | Energy / Frequency |
|---|---|---|
Undamped oscillation | SHM with constant amplitude | Total energy constant |
Damped oscillation | SHM with decreasing amplitude with time | Frequency decreases; time period increases |
▢ Read and Digest:
Table 1: Important SHM Points
Fact | Point |
|---|---|
Necessary and sufficient condition | |
Displacement direction | Away from mean position |
Acceleration in SHM | Changes both magnitude and direction |
If acceleration increases | Time period remains same |
SHM system requirement | Elasticity + inertia |
Uniform circular motion | Periodic but not SHM |
Constants in SHM | Time period, frequency, angular frequency, total energy, initial phase |
Variables in SHM | Displacement, velocity, acceleration, force, K.E., P.E. |
Second pendulum | Time period = 2 s; length = 99.29 cm |
Similarly charged horizontal sheet near charged bob | Time period increases |
Oppositely charged sheet near charged bob | Time period decreases |
Spring time period in accelerating vehicle | Same as stationary vehicle |
Simple pendulum in accelerating vehicle | Time period decreases |
Girl on swing stands up | Time period decreases |
Friend sits beside girl on swing | Time period remains same |
Change in amplitude | Does not change time period of simple pendulum |
Hollow sphere filled with water, water flows out | Period first increases then decreases |
Hollow sphere pendulum with mercury, little mercury drained | Time period increases |
Simple pendulum on Moon | |
Length-time period graph | Parabola |
Straight line |
▢ High-Yield Recall:
Table 1: SHM One-Liners
Fact | Answer |
|---|---|
Periodic motion | Position repeats after fixed time |
Oscillatory motion | To-and-fro motion about mean position |
SHM condition | |
Restoring force | |
Linear SHM equation | |
Angular SHM equation | |
Angular frequency | |
Displacement | |
Velocity | |
Acceleration | |
K.E. | |
P.E. | |
Total energy | |
At mean position | Velocity maximum; acceleration zero |
At extreme position | Velocity zero; acceleration maximum |
Velocity-displacement graph | Ellipse |
Acceleration-displacement graph | Straight line |
Simple pendulum time period | |
Spring time period | |
U-tube liquid time period | |
Earth tunnel time period | 84.6 min |
Earth tunnel centre time | 21 min |
Second pendulum length | 99.29 cm |
K.E. frequency | |
Total energy frequency | 0 |
Undamped oscillation | Constant amplitude |
Damped oscillation | Decreasing amplitude |
Q1.
Simple pendulum has amplitude R and period T. Time to move from y = R to y = R/2 is
📅CEE MBBS 2025
Q2.
The SHM of a particle is given by an equation y = 4 sinωt + 3 cosωt. The amplitude is:
📅CEE Nursing 2024
Q3.
The phase difference between velocity and acceleration in SHM is:
📅CEE BDS 2023
Q4.
In SHM, the period of oscillation of mass M suspended from a spring is 1 second, then time period of the oscillation of mass 4M will be:
📅CEE BDS 2021
Q5.
The graph plotted between acceleration and displacement in SHM will be a:
📅BP 2011
Q6.
Two bodies execute SHM simultaneously. Their resultant amplitude is maximum when their phase difference is:
📅BP 2009
Q7.
The time period of a simple pendulum is:
📅BP 2009
Q8.
📅MOE 2014
Q9.
The kinetic energy of a particle executing SHM when its displacement is one-third of its amplitude is:
📅MOE 2012
Q10.
If the kinetic energy of a body executing SHM is one-third of its potential energy, the displacement is approximately what percentage of the amplitude?
📅MOE 2009
Q11.
📅I.E. 2012
Q12.
For a body executing SHM, at the mean position:
📅I.E. 2012
Q13.
📅I.E. 2013
Q14.
📅IOM 2014
Q15.
The time period of a simple pendulum doubles when:
📅IOM 2012
Q16.
A pendulum eventually stops oscillating because of:
📅IOM 2011
Q17.
In SHM, the particle’s speed is minimum at the:
📅KU 2014
Q18.
A hollow sphere containing water is suspended by a thread and made to oscillate. As water slowly flows out of a small hole at the bottom, the period initially:
📅KU 2014
Q19.
A pendulum clock taken to high altitude will keep correct time if:
📅KU 2014
Q20.
📅KU 2012
Q21.
Q22.
The period of a simple pendulum doubles when:
📅IOM 2012
Q23.
Q24.
Q25.
A planet has twice Earth’s mass and twice Earth’s diameter. A pendulum that has period 1 s on Earth has period on this planet:
Q26.
A seconds pendulum has a period of 2 s with a 50 g hollow bob. The hollow bob is replaced by a 100 g solid bob of the same radius. The period becomes:
Q27.
A 1 kg weight extends a light spring by 9.8 cm. The period of oscillation is:
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📅IOM 2008
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📅BPKIHS
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📅BPKIHS
Q40.
📅I.E.•BPKIHS
Q41.
Q42.
The kinetic energy of a block oscillating on a spring is independent of:
Q43.
A simple pendulum’s period increases by 0.1% when taken to the peak of a mountain. If Earth’s radius is 6400 km, the peak’s height is approximately:
Q44.
A simple pendulum’s period increases by 0.01% when taken into a mine. For Earth’s radius 6400 km, estimate the depth of the mine:
Q45.
A body executes SHM. Its speeds at displacements 4 cm and 5 cm are 10 cm/s and 8 cm/s respectively. Find its period:
Q46.
A simple pendulum has a solid steel-sphere bob. If it is replaced by a hollow steel-sphere bob of the same mass and material, its period (with the suspension length unchanged) will:
Q47.
During SHM, when a particle lies midway between the mean and an extreme position, the ratio of kinetic to potential energy is:
Q48.
Q49.
Q50.
A simple harmonic oscillator has displacement 0.02 m and acceleration 2 m/s² at a particular instant. Its angular frequency is:
Q51.
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Q54.
Q55.
Two pendulums of lengths 1 m and 1.21 m start swinging together. How many oscillations will the longer pendulum complete before they next swing together in phase?
Q56.
If the length of a pendulum increases by 21%, its time period increases by:
Q57.
📅MOE 2009
Q58.
📅KU 2010
Q59.
The kinetic energy of a particle executing SHM is maximum at displacement equal to:
📅MOE 2066
Q60.
The period of a simple pendulum inside a satellite orbiting Earth is:
📅MOE 2063
Q61.
A tunnel passes through Earth’s centre. A stone dropped into it reaches the centre. At the centre, its:
📅MOE 2062
Q62.
📅MOE 2010
Q63.
A frictionless hole is bored along Earth’s diameter. When a ball is dropped into one end, it:
📅MOE 2061
Q64.
📅I.E. 2006
Q65.
If a simple pendulum’s length increases by 44%, its period increases by:
📅I.E. 2004
Q66.
📅BPKIHS 2009
Q67.
📅BPKIHS 2004
Q68.
📅BPKIHS 1996
Q69.
At which position during SHM is kinetic energy maximum?
📅KU 2016
Q70.
In SHM, kinetic energy is minimum at the:
📅KU 2017