A group of students was asked to use stroboscope to measure the speed of
shaft turning at 2880 rpm.The available flashing rates lie within the range of
24 to 96 per second. At what frequency setting it is expected to get a single,
double and triple image of distinguish mark made on the rotating shaft.
Answers
Answer:
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Single and double images of the distinguishing mark made on the shaft, are expected at 2880 per minute and 5760 per minute respectively. But, triple images are not possible.
Given,
A group of students are using stroboscope to measure the speed of a shaft.
The shaft is turning at 2880 rpm.
Available flashing rates range: from 24 to 96 per second.
To find,
At what frequency setting,
single, double, and triple images of the distinguishing mark made on the shaft, are expected.
Solution,
It can be seen that the shaft speed is given to be 2880 rpm.
Further, the flashing rates range is:
24 to 96 per second.
Firstly, we need to make both the speeds in similar units. So, converting flashing rates into rpm, we get the range
1440 to 5760 per minute.
Now, in a stroboscope,
- a single image of the reference mark appears at the same speed as that of the shaft (or the rotating object),
- two images appear at double the speed, and,
- three images will appear at triple speed, and so on.
Thus, here, we can see that,
a single image will appear at speed
= 2880 rpm.
2 images will appear at speed
= 2 × 2880
= 5760 rpm.
3 images should appear at speed
= 3 × 2880
= 8640
However, the available range is only from 1440 to 5760 per minute.
Hence, it is not possible to get triple images of the reference mark.
Therefore, single and double images of the distinguishing mark made on the shaft, are expected at 2880 per minute and 5760 per minute respectively. But, triple images are not possible.
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