Question 1 of 5
An engineer is analyzing a rotating camera mounted on a straight wall. The camera turns at a constant rate, and the angle it makes with the wall is always measured as the smaller angle. A sensor records the angle at different times, as shown in the table:
Time after start (seconds): , , ,
Angle with wall (degrees): , , ,
If the camera completed exactly one full rotation during the time shown in the table, what is the value of ?
Explanation
Because the camera rotates at a constant rate, its actual direction changes by equal amounts over equal time intervals. The times increase by seconds each: from to , from to , and from to .
The recorded angle is the smaller angle between the camera and the straight wall, so each recorded value must be between and . As the camera keeps rotating, that smaller angle increases up to and then decreases, repeating in a predictable way.
From to seconds, the recorded angle changes from to , an increase of . Since the turning rate is constant, in the next seconds the actual direction changes by the same amount.
At seconds, the camera is at to the wall. Adding gives an actual direction of relative to the wall's direction. But the sensor records the smaller angle with the wall, so it records
Thus, .
Check with the last value: from to seconds, another of rotation takes the actual direction from to . The smaller angle with the wall is
which matches the table. Therefore, the value of is .
Concept summary
When an angle with a line is defined as the smaller angle, the recorded measure stays between and , even though the actual direction may continue rotating past . Constant rotation means equal time intervals correspond to equal changes in actual direction, so the measured angle may increase and then decrease.