Projectile Motion of a Secondary Rocket in a Vertical Launch

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The discussion focuses on the projectile motion of a secondary rocket launched from a primary rocket traveling upward at 8.50 m/s. The secondary rocket is launched at 12 m/s at a 53-degree angle, with calculations for its horizontal and vertical velocity components provided. The velocities are analyzed from both the astronaut's perspective and Mission Control's perspective, yielding specific values for each component. The conversation confirms the calculations for part (a) of the homework, with participants expressing satisfaction with the results. The thread emphasizes understanding the dynamics of relative motion in a vertical launch scenario.
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Homework Statement



When it is 145 m above the ground, a rocket traveling vertically upward at a constant 8.50 m/s relative to the ground launches a secondary rocket at a speed of 12 m/s at an angle of 53 degrees above the horizontal, both quantities being measured by an astronaut sitting in the rocket. Air resistance is too small to worry about.

(a) Just as the secondary rocket is launched, what are the horizontal and vertical components of its velocity relative to (i) the astronaut sitting in the rocket and (ii) Mission Control on the ground?

(b) Find the initial speed and launch angle of the secondary rocket as measured by mission control.

(c) What maximum height above the ground does the secondary rocket reach?



Homework Equations



Vy=Vosin(θ)
Vx=Vocos(θ)

Vr2/e=Vr2/r1+Vr1/e

Vr2/e= velocity of rocket 2 relative to earth
Vr2/r1= velocity of rocket 2 relative to rocket 1
Vr1/e= velocity of rocket 1 relative to earth

The Attempt at a Solution


A)
i:
Vr2/r1-x= 12m/s*cos(53)=7.2217 m/s
Vr2/r1-y= 12m/s*sin(53)=9.5836 m/s

Vr2/e=vr2/r1 + vr1/e

ii: Vr2/e-y=vr2/r1-y + vr1/e-y
Vr2/3-y= 9.5836 m/s + 8.50m/s=18.0836m/s

Vr2/e-x=vr2/r1-x + vr1/e-x
vr2/e-x= 7.2217m/s + 0=7.2217m/s

Do I have part a right so far? thanks!
 
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Toranc3 said:
Do I have part a right so far? thanks!
Looks good to me!
 
Doc Al said:
Looks good to me!

Thank you Doctor!
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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