Answer:
43.17 ft/s
Step-by-step explanation:
Let the height of the wall is y.
distance of wall from light is 20 feet.
[tex]tan\theta =\frac{y}{20}[/tex]
y = 20 tanθ .... (1)
time period, T = 3 second
[tex]\frac{d\theta}{dt}=\frac{2\pi}{3}[/tex]
Differentiate equation (1) with respect to t.
[tex]\frac{dy}{dt}=20sec^{2}\theta\times \frac{d\theta}{dt}[/tex]
[tex]\frac{dy}{dt}=20sec^{2}10\times \frac{2\pi}{3}[/tex]
dy/dt = 20 x 2.16
dy/dt = 43.17 ft/s
