Damped motion and response time
Key idea: Damping transfers oscillation energy to other stores and reduces amplitude. Critical damping gives the fastest return to equilibrium without oscillation for a release from rest.
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Guided lessons · coming soon
Guided lesson
Guided steps
- Follow how resistive forces transfer energy out of the oscillation.
- Find the energy fraction remaining from the peak amplitudes.
- Explain where the lost oscillation energy goes.
- Compare overshoot and return time for the same release.
- Decide what each trace tells you about the damping.
- Suggest the setting and explain how to test it.
- Explain why suspension and meter pointers need fast, smooth recovery.
- Choose the damping for the fastest return without bouncing.
- Identify the original damping and explain how to improve the reading.
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ContinueA playground swing left alone slowly comes to rest, and a car that goes over a bump stops bouncing almost at once. Both are damped oscillations: resistive forces take energy out of the oscillation. How much damping there is decides whether the motion dies away slowly, settles quickly or creeps back, and a car’s suspension is designed to sit on the boundary between them.
What damping does
In a real oscillator, resistive forces such as air resistance, friction or the viscous drag of oil act against the motion. They do negative work on the oscillator, so its energy is gradually transferred to internal energy of the oscillator and its surroundings. This is damping. The amplitude decreases, because the energy of an oscillation is proportional to the square of its amplitude. The total energy is still conserved: it has moved to other stores, not been destroyed.
Check your understanding 1 Halving the amplitude
The peak amplitude of a lightly damped linear oscillator with unchanged mass and stiffness falls from 4.00 cm to 2.00 cm. What fraction of its energy of oscillation remains? Enter a decimal. Explain the energy destination in the next activity.
Show answer
The energy is proportional to the amplitude squared, so (2.00/4.00)² = 1/4 remains. The other three-quarters has been transferred, mainly to internal energy of the oscillator and the surrounding air.
Check your understanding 2 Account for the missing oscillation energy
Where has the other three-quarters of the energy gone? Explain why total energy is still conserved.
Show answer
Resistive forces do negative work on the oscillation, transferring its energy mainly to internal energy of the oscillator and surroundings. The oscillation has less mechanical energy, but the total energy of the oscillator and surroundings is conserved. Check that you name the larger system rather than saying energy is destroyed.
Light, critical and heavy damping
The graph shows the same oscillator, displaced by the same amount and released from rest, with three degrees of damping.
Damping after the same release from rest
Only the underdamped curve oscillates. Critical damping approaches equilibrium fastest among the non-oscillatory returns for the same mass, stiffness and initial conditions.
Scroll across the figure to read all labels.
View figure data
| Scaled time, ω₀t (unitless) | Under: ζ = 0.20 | Critical: ζ = 1 | Over: ζ = 2 |
|---|---|---|---|
| 0.00 | 1.000000 | 1.00000000 | 1.00000 |
| 0.05 | 0.998759 | 0.99879090 | 0.99883 |
| 0.10 | 0.995070 | 0.99532116 | 0.99561 |
| 0.15 | 0.988992 | 0.98981417 | 0.99072 |
| 0.20 | 0.980587 | 0.98247690 | 0.98447 |
| 0.25 | 0.969922 | 0.97350098 | 0.97712 |
| 0.30 | 0.957068 | 0.96306369 | 0.96889 |
| 0.35 | 0.942100 | 0.95132892 | 0.95996 |
| 0.40 | 0.925097 | 0.93844806 | 0.95047 |
| 0.45 | 0.906141 | 0.92456082 | 0.94055 |
| 0.50 | 0.885319 | 0.90979599 | 0.93029 |
| 0.55 | 0.862718 | 0.89427221 | 0.91979 |
| 0.60 | 0.838429 | 0.87809862 | 0.90911 |
| 0.65 | 0.812547 | 0.86137553 | 0.89830 |
| 0.70 | 0.785166 | 0.84419502 | 0.88742 |
| 0.75 | 0.756384 | 0.82664147 | 0.87650 |
| 0.80 | 0.726301 | 0.80879214 | 0.86558 |
| 0.85 | 0.695016 | 0.79071762 | 0.85467 |
| 0.90 | 0.662630 | 0.77248235 | 0.84381 |
| 0.95 | 0.629246 | 0.75414500 | 0.83300 |
| 1.00 | 0.594966 | 0.73575888 | 0.82226 |
| 1.05 | 0.559893 | 0.71737239 | 0.81161 |
| 1.10 | 0.524128 | 0.69902928 | 0.80105 |
| 1.15 | 0.487774 | 0.68076905 | 0.79059 |
| 1.20 | 0.450934 | 0.66262727 | 0.78024 |
| 1.25 | 0.413706 | 0.64463579 | 0.76999 |
| 1.30 | 0.376193 | 0.62682312 | 0.75986 |
| 1.35 | 0.338491 | 0.60921461 | 0.74984 |
| 1.40 | 0.300698 | 0.59183271 | 0.73994 |
| 1.45 | 0.262909 | 0.57469721 | 0.73016 |
| 1.50 | 0.225218 | 0.55782540 | 0.72049 |
| 1.55 | 0.187716 | 0.54123233 | 0.71095 |
| 1.60 | 0.150492 | 0.52493095 | 0.70153 |
| 1.65 | 0.113632 | 0.50893226 | 0.69222 |
| 1.70 | 0.077221 | 0.49324551 | 0.68304 |
| 1.75 | 0.041341 | 0.47787834 | 0.67397 |
| 1.80 | 0.006068 | 0.46283689 | 0.66502 |
| 1.85 | -0.028521 | 0.44812592 | 0.65618 |
| 1.90 | -0.062355 | 0.43374900 | 0.64746 |
| 1.95 | -0.095365 | 0.41970851 | 0.63885 |
| 2.00 | -0.127484 | 0.40600585 | 0.63036 |
| 2.05 | -0.158653 | 0.39264146 | 0.62198 |
| 2.10 | -0.188811 | 0.37961493 | 0.61371 |
| 2.15 | -0.217906 | 0.36692510 | 0.60554 |
| 2.20 | -0.245884 | 0.35457011 | 0.59749 |
| 2.25 | -0.272701 | 0.34254748 | 0.58954 |
| 2.30 | -0.298311 | 0.33085418 | 0.58170 |
| 2.35 | -0.322676 | 0.31948669 | 0.57396 |
| 2.40 | -0.345760 | 0.30844104 | 0.56632 |
| 2.45 | -0.367532 | 0.29771287 | 0.55879 |
| 2.50 | -0.387963 | 0.28729750 | 0.55135 |
| 2.55 | -0.407029 | 0.27718991 | 0.54402 |
| 2.60 | -0.424710 | 0.26738488 | 0.53678 |
| 2.65 | -0.440991 | 0.25787693 | 0.52963 |
| 2.70 | -0.455857 | 0.24866040 | 0.52259 |
| 2.75 | -0.469301 | 0.23972948 | 0.51563 |
| 2.80 | -0.481318 | 0.23107824 | 0.50877 |
| 2.85 | -0.491905 | 0.22270064 | 0.50200 |
| 2.90 | -0.501066 | 0.21459056 | 0.49532 |
| 2.95 | -0.508805 | 0.20674184 | 0.48873 |
| 3.00 | -0.515132 | 0.19914827 | 0.48222 |
| 3.05 | -0.520059 | 0.19180364 | 0.47581 |
| 3.10 | -0.523601 | 0.18470173 | 0.46948 |
| 3.15 | -0.525778 | 0.17783633 | 0.46323 |
| 3.20 | -0.526610 | 0.17120126 | 0.45706 |
| 3.25 | -0.526122 | 0.16479038 | 0.45098 |
| 3.30 | -0.524343 | 0.15859762 | 0.44498 |
| 3.35 | -0.521301 | 0.15261694 | 0.43906 |
| 3.40 | -0.517029 | 0.14684239 | 0.43321 |
| 3.45 | -0.511562 | 0.14126808 | 0.42745 |
| 3.50 | -0.504938 | 0.13588823 | 0.42176 |
| 3.55 | -0.497195 | 0.13069711 | 0.41615 |
| 3.60 | -0.488375 | 0.12568912 | 0.41061 |
| 3.65 | -0.478521 | 0.12085875 | 0.40515 |
| 3.70 | -0.467678 | 0.11620057 | 0.39975 |
| 3.75 | -0.455893 | 0.11170929 | 0.39443 |
| 3.80 | -0.443212 | 0.10737970 | 0.38918 |
| 3.85 | -0.429686 | 0.10320672 | 0.38400 |
| 3.90 | -0.415365 | 0.09918537 | 0.37889 |
| 3.95 | -0.400299 | 0.09531077 | 0.37385 |
| 4.00 | -0.384541 | 0.09157819 | 0.36888 |
| 4.05 | -0.368143 | 0.08798299 | 0.36397 |
| 4.10 | -0.351160 | 0.08452064 | 0.35912 |
| 4.15 | -0.333643 | 0.08118674 | 0.35434 |
| 4.20 | -0.315647 | 0.07797700 | 0.34963 |
| 4.25 | -0.297227 | 0.07488723 | 0.34498 |
| 4.30 | -0.278436 | 0.07191336 | 0.34039 |
| 4.35 | -0.259328 | 0.06905145 | 0.33586 |
| 4.40 | -0.239957 | 0.06629764 | 0.33139 |
| 4.45 | -0.220375 | 0.06364819 | 0.32698 |
| 4.50 | -0.200636 | 0.06109948 | 0.32262 |
| 4.55 | -0.180791 | 0.05864798 | 0.31833 |
| 4.60 | -0.160892 | 0.05629028 | 0.31409 |
| 4.65 | -0.140988 | 0.05402305 | 0.30991 |
| 4.70 | -0.121130 | 0.05184308 | 0.30579 |
| 4.75 | -0.101366 | 0.04974725 | 0.30172 |
| 4.80 | -0.081741 | 0.04773253 | 0.29771 |
| 4.85 | -0.062304 | 0.04579601 | 0.29374 |
| 4.90 | -0.043096 | 0.04393484 | 0.28983 |
| 4.95 | -0.024163 | 0.04214628 | 0.28598 |
| 5.00 | -0.005544 | 0.04042768 | 0.28217 |
| 5.05 | 0.012719 | 0.03877647 | 0.27842 |
| 5.10 | 0.030589 | 0.03719015 | 0.27471 |
| 5.15 | 0.048030 | 0.03566634 | 0.27105 |
| 5.20 | 0.065007 | 0.03420270 | 0.26745 |
| 5.25 | 0.081486 | 0.03279699 | 0.26389 |
| 5.30 | 0.097438 | 0.03144704 | 0.26038 |
| 5.35 | 0.112832 | 0.03015076 | 0.25691 |
| 5.40 | 0.127643 | 0.02890612 | 0.25349 |
| 5.45 | 0.141844 | 0.02771117 | 0.25012 |
| 5.50 | 0.155413 | 0.02656401 | 0.24679 |
| 5.55 | 0.168329 | 0.02546284 | 0.24351 |
| 5.60 | 0.180573 | 0.02440590 | 0.24027 |
| 5.65 | 0.192127 | 0.02339149 | 0.23707 |
| 5.70 | 0.202977 | 0.02241797 | 0.23391 |
| 5.75 | 0.213110 | 0.02148377 | 0.23080 |
| 5.80 | 0.222515 | 0.02058737 | 0.22773 |
| 5.85 | 0.231183 | 0.01972731 | 0.22470 |
| 5.90 | 0.239107 | 0.01890217 | 0.22171 |
| 5.95 | 0.246283 | 0.01811059 | 0.21876 |
| 6.00 | 0.252707 | 0.01735127 | 0.21585 |
| 6.05 | 0.258379 | 0.01662293 | 0.21297 |
| 6.10 | 0.263298 | 0.01592436 | 0.21014 |
| 6.15 | 0.267469 | 0.01525439 | 0.20734 |
| 6.20 | 0.270896 | 0.01461190 | 0.20458 |
| 6.25 | 0.273584 | 0.01399579 | 0.20186 |
| 6.30 | 0.275542 | 0.01340502 | 0.19917 |
| 6.35 | 0.276779 | 0.01283859 | 0.19652 |
| 6.40 | 0.277307 | 0.01229552 | 0.19391 |
| 6.45 | 0.277138 | 0.01177489 | 0.19133 |
| 6.50 | 0.276286 | 0.01127579 | 0.18878 |
| 6.55 | 0.274768 | 0.01079737 | 0.18627 |
| 6.60 | 0.272600 | 0.01033880 | 0.18379 |
| 6.65 | 0.269800 | 0.00989927 | 0.18134 |
| 6.70 | 0.266388 | 0.00947802 | 0.17893 |
| 6.75 | 0.262385 | 0.00907432 | 0.17655 |
| 6.80 | 0.257811 | 0.00868745 | 0.17420 |
| 6.85 | 0.252690 | 0.00831673 | 0.17188 |
| 6.90 | 0.247045 | 0.00796150 | 0.16959 |
| 6.95 | 0.240901 | 0.00762115 | 0.16734 |
| 7.00 | 0.234281 | 0.00729506 | 0.16511 |
| 7.05 | 0.227214 | 0.00698264 | 0.16291 |
| 7.10 | 0.219724 | 0.00668335 | 0.16075 |
| 7.15 | 0.211838 | 0.00639664 | 0.15861 |
| 7.20 | 0.203585 | 0.00612200 | 0.15650 |
| 7.25 | 0.194991 | 0.00585894 | 0.15441 |
| 7.30 | 0.186084 | 0.00560697 | 0.15236 |
| 7.35 | 0.176894 | 0.00536565 | 0.15033 |
| 7.40 | 0.167448 | 0.00513452 | 0.14833 |
| 7.45 | 0.157774 | 0.00491318 | 0.14636 |
| 7.50 | 0.147902 | 0.00470122 | 0.14441 |
| 7.55 | 0.137859 | 0.00449824 | 0.14249 |
| 7.60 | 0.127674 | 0.00430388 | 0.14059 |
| 7.65 | 0.117374 | 0.00411778 | 0.13872 |
| 7.70 | 0.106988 | 0.00393960 | 0.13687 |
| 7.75 | 0.096543 | 0.00376900 | 0.13505 |
| 7.80 | 0.086066 | 0.00360567 | 0.13325 |
| 7.85 | 0.075583 | 0.00344930 | 0.13148 |
| 7.90 | 0.065121 | 0.00329962 | 0.12973 |
| 7.95 | 0.054705 | 0.00315633 | 0.12800 |
| 8.00 | 0.044359 | 0.00301916 | 0.12630 |
| 8.05 | 0.034109 | 0.00288787 | 0.12462 |
| 8.10 | 0.023977 | 0.00276221 | 0.12296 |
| 8.15 | 0.013987 | 0.00264193 | 0.12133 |
| 8.20 | 0.004160 | 0.00252681 | 0.11971 |
| 8.25 | -0.005483 | 0.00241664 | 0.11812 |
| 8.30 | -0.014921 | 0.00231121 | 0.11655 |
| 8.35 | -0.024136 | 0.00221031 | 0.11499 |
| 8.40 | -0.033108 | 0.00211375 | 0.11346 |
| 8.45 | -0.041821 | 0.00202136 | 0.11195 |
| 8.50 | -0.050258 | 0.00193295 | 0.11046 |
| 8.55 | -0.058403 | 0.00184836 | 0.10899 |
| 8.60 | -0.066243 | 0.00176742 | 0.10754 |
| 8.65 | -0.073763 | 0.00168997 | 0.10611 |
| 8.70 | -0.080952 | 0.00161588 | 0.10470 |
| 8.75 | -0.087798 | 0.00154500 | 0.10331 |
| 8.80 | -0.094291 | 0.00147718 | 0.10193 |
| 8.85 | -0.100423 | 0.00141231 | 0.10058 |
| 8.90 | -0.106184 | 0.00135025 | 0.09924 |
| 8.95 | -0.111569 | 0.00129088 | 0.09792 |
| 9.00 | -0.116571 | 0.00123410 | 0.09661 |
| 9.05 | -0.121185 | 0.00117978 | 0.09533 |
| 9.10 | -0.125409 | 0.00112782 | 0.09406 |
| 9.15 | -0.129238 | 0.00107813 | 0.09281 |
| 9.20 | -0.132671 | 0.00103060 | 0.09157 |
| 9.25 | -0.135709 | 0.00098514 | 0.09035 |
| 9.30 | -0.138350 | 0.00094167 | 0.08915 |
| 9.35 | -0.140597 | 0.00090009 | 0.08796 |
| 9.40 | -0.142451 | 0.00086033 | 0.08679 |
| 9.45 | -0.143916 | 0.00082231 | 0.08564 |
| 9.50 | -0.144996 | 0.00078594 | 0.08450 |
| 9.55 | -0.145695 | 0.00075117 | 0.08337 |
| 9.60 | -0.146021 | 0.00071792 | 0.08227 |
| 9.65 | -0.145978 | 0.00068613 | 0.08117 |
| 9.70 | -0.145575 | 0.00065573 | 0.08009 |
| 9.75 | -0.144820 | 0.00062667 | 0.07902 |
| 9.80 | -0.143721 | 0.00059888 | 0.07797 |
| 9.85 | -0.142289 | 0.00057231 | 0.07693 |
| 9.90 | -0.140532 | 0.00054690 | 0.07591 |
| 9.95 | -0.138463 | 0.00052262 | 0.07490 |
| 10.00 | -0.136092 | 0.00049940 | 0.07390 |
| 10.05 | -0.133431 | 0.00047720 | 0.07292 |
| 10.10 | -0.130493 | 0.00045598 | 0.07195 |
| 10.15 | -0.127290 | 0.00043570 | 0.07099 |
| 10.20 | -0.123835 | 0.00041631 | 0.07005 |
| 10.25 | -0.120143 | 0.00039777 | 0.06912 |
| 10.30 | -0.116226 | 0.00038005 | 0.06820 |
| 10.35 | -0.112099 | 0.00036312 | 0.06729 |
| 10.40 | -0.107776 | 0.00034693 | 0.06639 |
| 10.45 | -0.103273 | 0.00033146 | 0.06551 |
| 10.50 | -0.098602 | 0.00031667 | 0.06464 |
| 10.55 | -0.093781 | 0.00030253 | 0.06378 |
| 10.60 | -0.088823 | 0.00028903 | 0.06293 |
| 10.65 | -0.083743 | 0.00027611 | 0.06209 |
| 10.70 | -0.078556 | 0.00026378 | 0.06126 |
| 10.75 | -0.073278 | 0.00025198 | 0.06045 |
| 10.80 | -0.067923 | 0.00024071 | 0.05964 |
| 10.85 | -0.062506 | 0.00022994 | 0.05885 |
| 10.90 | -0.057041 | 0.00021965 | 0.05807 |
| 10.95 | -0.051544 | 0.00020982 | 0.05730 |
| 11.00 | -0.046028 | 0.00020042 | 0.05653 |
| 11.05 | -0.040507 | 0.00019144 | 0.05578 |
| 11.10 | -0.034995 | 0.00018286 | 0.05504 |
| 11.15 | -0.029506 | 0.00017466 | 0.05431 |
| 11.20 | -0.024053 | 0.00016683 | 0.05358 |
| 11.25 | -0.018648 | 0.00015934 | 0.05287 |
| 11.30 | -0.013303 | 0.00015219 | 0.05217 |
| 11.35 | -0.008032 | 0.00014535 | 0.05147 |
| 11.40 | -0.002845 | 0.00013882 | 0.05079 |
| 11.45 | 0.002246 | 0.00013259 | 0.05011 |
| 11.50 | 0.007231 | 0.00012663 | 0.04944 |
| 11.55 | 0.012099 | 0.00012093 | 0.04879 |
| 11.60 | 0.016840 | 0.00011549 | 0.04814 |
| 11.65 | 0.021447 | 0.00011030 | 0.04750 |
| 11.70 | 0.025909 | 0.00010533 | 0.04686 |
| 11.75 | 0.030218 | 0.00010059 | 0.04624 |
| 11.80 | 0.034368 | 0.00009606 | 0.04563 |
| 11.85 | 0.038350 | 0.00009173 | 0.04502 |
| 11.90 | 0.042158 | 0.00008760 | 0.04442 |
| 11.95 | 0.045787 | 0.00008365 | 0.04383 |
| 12.00 | 0.049230 | 0.00007987 | 0.04324 |
- Light damping (underdamping): the body keeps oscillating, and the amplitude decreases gradually. The period stays almost the same.
- Critical damping: the body returns to equilibrium in the shortest possible time without oscillating, that is, without overshooting.
- Heavy damping (overdamping): the body does not oscillate, but it creeps back to equilibrium more slowly than with critical damping.
More damping is not always quicker. Beyond critical damping, extra damping slows the return.
Worked example 1
Three settings of one damper
Problem
The same spring and mass are pulled down 4.00 cm and released from rest, with three settings P, Q and R of an adjustable damper. P passes through equilibrium several times. Q and R do not pass through equilibrium, and Q returns sooner than R. What can you say about the damping in each case?
Show full solution
Setting P
Method
Look for oscillation.Reason
Only a lightly damped body oscillates.Working
Answer
P is lightly damped.
Settings Q and R
Reason
Neither oscillates, and the same system was released in the same way, so their return times can be compared.Working
Answer
Both are critically or heavily damped, and R is more heavily damped than Q, because it is slower.
How far you can go
Working
Answer
You cannot say Q is exactly critical. To find critical damping, reduce the damping step by step: the last setting before the body starts to overshoot is critical.
Check your understanding 3 Two door closers
A door closer returns without overshooting. When its damping is reduced slightly, the door overshoots its resting position. What does this suggest about the original setting? How would you test the suggestion using the same door and starting position?
Show answer
The original setting is close to critical damping, because a slightly smaller damping allows oscillation. To locate the boundary more precisely, vary the damping in small steps while using the same door, spring and starting position. Find the smallest setting that returns without overshooting. Repeat with smaller changes to locate the setting more closely.
Why critical damping matters
When a car goes over a bump, its springs start the body oscillating. Shock absorbers damp the oscillation. Close to critical damping, the car returns to its normal level quickly without bouncing up and down. Light damping would leave the car bouncing; heavy damping would make the suspension slow to recover, so the car would ride on compressed springs after a series of bumps. The pointers of analogue meters are damped close to critically for the same reason: they settle on the reading quickly without swinging past it.
Spot the mistake 2
As much damping as possible?
Problem
A learner says a car suspension should have as much damping as possible, because more damping always makes the car settle faster after a bump. Which degree of damping should the suspension have?
Choose the damping
Show solution step by step
Too much damping
Reason
Beyond critical damping, the extra resistance slows the return to equilibrium.Working
Answer
Very heavy damping makes the car slow to recover from a bump.
The right amount
Working
Answer
Critical damping returns the car to its level in the shortest time without bouncing.
Common mistake
Stopping the bouncing is not the only aim: the suspension must also recover quickly. More damping helps only up to the critical value.
Check your understanding 4 A slow meter pointer
A meter pointer released from rest returns to its new equilibrium without overshooting. Reducing the damping makes it return faster, still without overshooting. What does this tell you about the original setting? Explain how to choose a setting for rapid readings without repeated swings.
Show answer
The original setting is heavily damped: a smaller damping still prevents overshoot and returns faster. Tune towards the boundary between overshooting and non-overshooting motion, keeping the same pointer and starting displacement. Close to critical damping gives the fastest non-oscillatory return; very heavy damping delays the reading. Check that your inference uses the changed setting, not just the absence of overshoot.
Common mistakes
- Saying damping destroys energy; it transfers energy to internal energy.
- Thinking more damping always means a quicker return.
- Identifying critical damping only from the absence of oscillation.
- Comparing damping in two different systems released in different ways.
Spotted an error? Report a correction
Syllabus and review details
- GCE A-Level H2 Physics 2027 · 2027
Content Overview, PDF pages 9–10; Subject Content, PDF pages 11–30
Last reviewed: