Sinusoidal Word Problems: The Basics
When tackling sinusoidal word problems, we need to identify key values like amplitude (half the distance from maximum to minimum), period (time for one complete cycle), and vertical shift (the middle value).
Let's look at a ferris wheel example: If the highest point is 43 feet high, the wheel has a 40-foot diameter, and completes one rotation every 8 seconds, we can create an equation. The wheel's middle height is 23 feet (highest point minus radius), making our amplitude 20 feet. Since the period is 8 seconds, we use either:
- Using cosine: y = -20cosπ/4⋅x + 23
- Using sine: y = 20sinπ/4⋅x + 23
💡 Remember this pattern: For anything moving in circles (wheels, gears, etc.), the period relates to angular velocity with B = 2π/period, and the amplitude equals the radius!
For objects like bicycle tires with nails, we follow the same process. A 20 cm radius tire making one rotation every 750 ms means the nail's height follows either y = 20cos8π/3⋅x + 20 or y = 20sin8π/3(x−1875) + 20. The coefficient 8π/3 comes from converting the period to radians (2π/0.75).