A photographer wants to capture Polaris, the North Star, and the surrounding stars without capturing any “star trails” caused by the rotation of the earth. He needs to use a long exposure (keep the shutter open for an extended period of time) to ensure that the stars show up bright and clear, but he will need his camera to rotate at the same rate as the earth to prevent the star trails from appearing in the photos.

Question

A photographer wants to capture Polaris, the North Star, and the surrounding stars without capturing any “star trails” caused by the rotation of the earth. He needs to use a long exposure (keep the shutter open for an extended period of time) to ensure that the stars show up bright and clear, but he will need his camera to rotate at the same rate as the earth to prevent the star trails from appearing in the photos.

Stars appear to rotate about Polaris at a rate of 14°
per minute. You can use this rate to write and solve equations. The photographer says that the stars will rotate a total of 15° while his camera shutter is open. The equation 14s=15
, where s is the length of time in minutes the shutter remains open, represents this situation. How long will the photographer’s camera shutter be open?

Question
Solve the equation 14s=15 for s.

Enter your answers in the boxes.

s =

The camera shutter will be open
min.

Answer 1

To solve the equation 14s = 15 for s, we need to isolate s by dividing both sides of the equation by 14:

14s/14 = 15/14

s = 15/14

So, the length of time the shutter will remain open is 15/14 minutes.

The camera shutter will be open for approximately 1.07 minutes.