samigupta8
  • samigupta8
A balloon is at a height of 81 m is ascending upward with a velocity of 12 ms1. A body of 2 kg weight is dropped from it. If g = 10 ms2, the body will reach the surface of earth in A) 1.5 sec B) 4.0 sec C) 5.4 sec D) 6.7 sec
Physics
  • Stacey Warren - Expert brainly.com
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SOLVED
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katieb
  • katieb
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anonymous
  • anonymous
\[h=h_0+v_0t-\frac{ 1 }{ 2 }g·t^2\].Surface will be hit when h=0, then solve:\[h_0+v_0t-\frac{ 1 }{ 2 }g·t^2=0\rightarrow 81+12t-5t^2=0\]Solutions are t=-3 and t=5.4. Definitely, for obvious reasons we have to discard t=-3, then the solution is t=5.4
anonymous
  • anonymous
Another way is finding anergy balance: The total initial energy is potential (mgh) plus kinetic (1/2mv^2) When it hits the ground, it is only kinetic, then:\[mgh_0+\frac{ 1 }{ 2 }mv_0^2=\frac{ 1 }{ 2 }mv_f^2 \rightarrow v_f=\sqrt{2gh_0+v_0^2}=\sqrt{1764}=42\]Initial velocity is upwards (we will consider it is positive) and Vf (velocity when hitting the ground is negative) is downwards, then we need to find t in: \[-v_f=v_0-g·t \rightarrow t=\frac{ v_0+v_f }{ g }=\frac{ 12+42 }{ 10 }=5.4\]
samigupta8
  • samigupta8
in the figure shown blocks A and B move with velocities v1 and v2 along horizontal direction.Find the ratio of v1 and v2|dw:1378143413384:dw|

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anonymous
  • anonymous
Please, a new question is a new post and do not forget to award medals if you have got a satisfactory answer. We are not here for accolades but what is fair is fair
samigupta8
  • samigupta8
bt i m unable to post it as a new question
anonymous
  • anonymous
Justo close this one and go to "ask a question..." prompt, top left of your screen
samigupta8
  • samigupta8
no no i m unable to copy the diagram of this question
anonymous
  • anonymous
I can do it, by the way, top of the drawing , is it a pulley?
samigupta8
  • samigupta8
yaa
samigupta8
  • samigupta8
bt how r u going to do it??
anonymous
  • anonymous
well, try to draw it again in a new post
samigupta8
  • samigupta8
bt how dat's wt i m asking there is no option of draw in that?
samigupta8
  • samigupta8
bt the answer is v1/v2=cosθ 2/cosθ 1
anonymous
  • anonymous
You are right, I made a mistake dividing by cos(theta) to get Vr, it is multiplying
samigupta8
  • samigupta8
bt how i got your answer when i was solving

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