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Speed of Objects

by Physics Novice
Tags: objects, speed
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Physics Novice
#1
Sep6-13, 06:48 AM
P: 1
As a stationary object, is it possible to determine the speed of an object as it approaches you? If so, how? ...and with accuracy?

For instance, if I'm standing on the sidewalk, can I determine the speed of a car on the road as it approaches me?
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Nugatory
#2
Sep6-13, 07:02 AM
Sci Advisor
Thanks
P: 3,713
Quote Quote by Physics Novice View Post
As a stationary object, is it possible to determine the speed of an object as it approaches you? If so, how? ...and with accuracy?

For instance, if I'm standing on the sidewalk, can I determine the speed of a car on the road as it approaches me?
Sure. Around here the traffic police use hand-held radar guns to catch speeders.
CWatters
#3
Sep6-13, 07:27 AM
P: 3,139
Time how long it takes the car to cover the distance between two objects (eg two lamp posts). Later measure the distance between the two lamp posts. Calculate the speed. The accuracy will be limited to how accurately you can measure the time. If the car casts a shadow on the lamp posts as it passes I'd suggest you can get quite an accurate measurement.

DennisN
#4
Sep6-13, 08:03 AM
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P: 483
Speed of Objects

Quote Quote by Physics Novice View Post
As a stationary object, is it possible to determine the speed of an object as it approaches you? If so, how? ...and with accuracy?
Some pictures and info to go along with Nugatory's reply: Doppler effect, Police RADAR.


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