so confused need help Thie Ques This Test: A helieogter is rising stralght p in

Question

so confused need help

Thie Ques This Test: A helieogter is rising stralght p in the air. Jus dislans from the ground t seoonds after take () How long will it take fur the helicopter to rise to l6 feet? ) Find the velocity and wexderation of the helicoposr when it i is 16 feet sbove the grou (a) The time it wall take fir the helicopter to rise o lo feet is seconds. (b) When the belicoptec is 16 feet ahew: th: grond, its velocity is fl r second When the helicopter is l6 fesi abave the ground, its acaceleration is ct per secund squan

Explanation / Answer

(a) Given, s(t)=2t^2+4t

Time to reach at height s=16ft

16 = 2 t^2 +4 t => 2t^2+4t-16=0 => t^2+2t-8=0

=> (t-2)(t+4)=0

=> t=2 or, t=-4 but time can not be negative

therfore t=2 sec

b) velocity=v=d(s)/dt=d(2t^2+4t)/dt

=> v(t) = 4t + 4

We know when helocopter is at height s=16, t=2

therefore, v(2) = 4*2 + 4=12 ft/sec

Accelaration=a(t)=dv(t)/dt=d(4t+4)/dt=4 ft/sec^2

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