Purchase Solution

Strobe Light on a Fan

Not what you're looking for?

1. A strobe lights shines on a fan. By changing the speed of the strobe light, the fan appeared to run slower and sometimes even looked like it was stopping or running backwards. Assume the fan has three identical blades so that once the fan has rotated 1/3 around it looks exactly the same. Before turning on the strobe light we notice that the fan rotates at a rate of 120 rotations per minute (RPM).

b. If we define the period of the fan as the time it takes for the fan to rotate and appear to return to its "starting position", what is the frequency of the fan (Hz)?
c. At what minimum rate (in Hz) should we run the strobe light so that the fan appears to rotate at a speed of 120 RPM?
e. What is the rotation rate of the fan in deg/second?
f. If the fan appears to run backward at a rate of 30 deg/flash calculate one possible strobe light flash rate.

Solution Summary

This solution provides a description of a strobe light on a fan. The rotation rate of the fan in deg/second is determined.

Solution Preview

(b)
The frequency is the number of rotations per second = (number of rotations per minute)/(60 seconds) =
120 round/min / ( 60 sec/min) = 2 (round/sec) = 2 Hz,
and the period is T = 1/(2 Hz) = (1/2) sec

(c)
This is a somewhat psychological question on how we get the impression on how the fan rotates.
The likely answer seems to ...

Basic Physics

This quiz will test your knowledge about basic Physics.

Intro to the Physics Waves

Some short-answer questions involving the basic vocabulary of string, sound, and water waves.

Introduction to Nanotechnology/Nanomaterials

This quiz is for any area of science. Test yourself to see what knowledge of nanotechnology you have. This content will also make you familiar with basic concepts of nanotechnology.

The Moon

Test your knowledge of moon phases and movement.

Variables in Science Experiments

How well do you understand variables? Test your knowledge of independent (manipulated), dependent (responding), and controlled variables with this 10 question quiz.