What was the speed of the projectile when it left the cannon?

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Homework Help Overview

The problem involves a projectile launched from the Earth's surface, reaching a height of 35,000 m. The objective is to determine the speed of the projectile at launch using gravitational concepts.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the meaning of variables in the equations, particularly the mass of the Earth and its implications for the problem. There is mention of using conservation of energy principles to relate potential and kinetic energy.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the variables involved and questioning the assumptions made in the problem setup. Some guidance on using conservation of energy has been provided, but there is no consensus on the correct approach yet.

Contextual Notes

Participants note the absence of mass in the initial setup and express uncertainty about how to proceed with the calculations based on the given information.

msattar07
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Homework Statement



A projectile is shot from the surface of te Earth by means of a very powerful cannon. If the projectile reaches a height of 35,000 m above Earth's surface, what was the speed of the projectile when it left the cannon?

a. 355 m/s
b. 827 m/s
c. 710 m/s
d. 906 m/s

Homework Equations



v= square root of GM/r

The Attempt at a Solution



there's no mass, so i wasnt sure how to solve it exactly
 
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What does capital M denote?
 
mass of the Earth
 
Well, that's not an unknown mass.
 
yea so i plugged it in but didnt get the right answer.

the answer is suppose to be B.
 
Well, use conservation of energy:

[tex]U_0 + K_0 = U_f + K_f[/tex]

You know that [tex]U = -\frac{GmM}{r}[/tex]
 

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