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a spy uses a telescope to track a rocket launched vertically from a launching pad 6 kmaway. At a certain moment, the angle (θ) between the telescope and the the ground is equal to π3 and is changing at a rate of 0.9 rad/min. What is the rocket’s velocity atthat moment?

Answer :

jolis1796

Answer:

v = 21.6 Km/min

Step-by-step explanation:

x = 6 Km

∅ = π/3 (variable)

d∅/dt = 0.9 rad/min

Let ∅ be the angle between the spy's line of sight and the ground and y is the distance between the rocket and the ground.

Then we have the equation

tan ∅ = y / x

⇒ (tan ∅)' = (y / x)' = (1/x)*y'

⇒ Sec²∅*(d∅/dt) = (1/x)*(dy/dt) = (1/x)*v

⇒ v = x*Sec²∅*(d∅/dt)

⇒ v = 6 Km*Sec²(π/3)*(0.9 rad/min)

⇒ v = 21.6 Km/min

Lanuel

Based on the calculations, the rocket’s velocity at this moment is equal to 21.6 km/min.

Given the following data:

  • Vertical distance = 6 kilometers.
  • Angle of inclination = [tex]\frac{\pi}{3}[/tex]
  • Rate of change = 0.9 rad/min.

How to calculate rocket’s velocity.

First of all, we would assign a variable to the given parameters. So, let the angle formed between the ground and the spy's line of sight be [tex]\theta[/tex] while the vertical distance between the rocket and the ground would be y.

From Tan trigonometric function, we have:

[tex]Tan \theta =\frac{y}{x}[/tex]

[tex]Tan\theta' = (\frac{y}{x} )'= \frac{1}{x} \times y'[/tex]

Note: In a right-angled triangle, the secant (sec) of an angle is equal to the ratio of the length of the hypotenuse to the length of the adjacent side.

[tex]Sec^2\theta(\frac{d\theta }{dt} )=\frac{1}{x} (\frac{dy}{dt} )=\frac{1}{x}(v)=\frac{v}{x}[/tex]

Cross-multiplying, we have:

[tex]V= xSec^2\theta(\frac{d\theta }{dt} )\\\\V= 6 \times Sec^2(\frac{\pi }{3} )\times 0.9\\\\V= 6 \times Sec^2(\frac{180 }{3} )\times 0.9[/tex]

Velocity, V = 21.6 km/min.

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