Determine the time required for a missile to reach its maximum altitude of 21 km

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SUMMARY

The discussion focuses on calculating the time required for a missile to reach its maximum altitude of 21 km, specifically in the context of the U-2 spy plane's capabilities. The relevant equation used is d = v_i t + 1/2 at^2, where d is the distance (21,000 m), a is the acceleration (-9.81 m/s²), and v_i is the initial velocity (0 m/s). The participants highlight the lack of specific information regarding the missile's speed and acceleration, leading to confusion in determining time. Ultimately, they suggest using the quadratic formula to solve for time, acknowledging the limitations due to missing variables.

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Homework Statement


The U-2 was an American spy plane capable of flying up to 21 km high at speeds over 600km/h. Determine the time required for the missile to reach its maximum altitude of the U-2.

Homework Equations


d=v_i t+1/2 at^2

The Attempt at a Solution


d=21000m
a=-9.81m/s^2
v_i=0
t=?

I don't know how to get time by itself and I have tried using the quadratic formula.
 
Last edited:
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i'm confused by this question. there is a missle but you are given no information as its speed (initial or final), or it's acceleration? something is missing here. if the only thing you know is the distance (21000m) then the best you can accomplish is an equation made up of the unknown variables.

there is little more you can do without any other info. you would not use the acceleration due to gravity as there is no suggestion that anything is falling - you only indicate that a missile is headed upwards.

EDIT: the best answer you can probably get is to solve the quadratic:

1/2at^2 + Vi - 2100 = 0

there use -b +/- sqrt( b^2 - 4ac) / 2a
 

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