Question

A group of rowdy teenagers near a wind turbine decide to place a pair of

Answer 1

Answer:

a) Hence the equation of the sinusoidal function that describes the height of the shorts in terms of time is $y = 9 + 7* sin(\pi * t / 15 - \pi / 6)$

b) Hence the height of the shorts at exactly t = 10 minutes, to

the nearest tenth of a meter is 5.5 meters

Step-by-step explanation:

a) The wind turbine blade traverses a circular path as it rotates with time (t), whose time variation is given by the following trajectory equation :

$x^2 + (y-yc)^2 = R^2$ ,

where  

R = (16 m - 2 m)/2 (since diameter = maximum height - minimum height of the pink short)

= 14 m / 2

= 7 m (radius of the circle)

Also, center of the circle will be at (0, 2 + R) i.e (0,9)

So,  is the trajectory path equation to the circle

Let $x = 7* cos(w*t + \phi ) & y = 9 + 7* sin(w* t + \phi)$ be the parametric form of the above circle equation which represent the position of the pink shorts at the tip of the blade at time t  

At t= 10s, y = 16 m so we have,

$9 + 7 * sin(10* w + \phi) = 16$ ---------------(1)

Also, at t= 25s, y =2 m so we have,

$9 + 7* sin(25 * w +\phi) = 2$--------------(2)

Solving we have, $10* w + \phi = \pi/2 & 25*w + \phi = 3*pi/2$

$15* w = \pi\\\\w = \pi/15 & \phi = \pi/2 - 10*\pi/15 = -\pi / 6$  

Therefore $y = 9 + 7* sin(\pi * t / 15 - \pi / 6)$ is the instantaneous height of the pink short at time t ( in seconds)

b) At t= 10minutes = 10 * 60 s = 600s, we have,

$y = 9 + 7 * sin(\pi * 600/15 - \pi / 6)\\\\= 9 + 7 * sin(40* \pi - \pi / 6)$

= 5.5 meters (pink short will be at 5.5 meters above ground level at t= 10 minutes)