Beginner Physics help?

[kaoriz]

Hi, I recently started physics and I am so lost!

 

I need to calculate the exact act of a cannon firing a projectile at series of targets a known distance away.

 

Here's what I know:

muzzle velocity of cannon: 31 meters/second

cannon length: 1.143 meters

The targets are, 50 m, 75 m, and 100 m, away.

 

What equation(s) do I use to calculate the launch angles?

 

Any help is greatly appreciated! =D

[foodchain]

http://www.globalsecurity.org/military/library/policy/army/fm/6-40/Ch7.htm

 

The above link is a bit of a mess but it contains a brief outline I think of artillery stuff, which if you use the words such as mussel velocity in connection with say google and or wikipedia should be able to help you, not that wikipedia is a search engine.

[big314mp]

I think he was looking for equations, rather than firing tables

 

In any case, this is a rather involved problem. If I am interpreting correctly, you will need to take into account:

 

1) The length of the cannon, assuming that the base of the cannon is at 0m. You need to calculate how high the end of the barrel is from the ground. This is your starting y displacement. You need to calculate how close the barrel of the cannon is to the target. This is your x displacement. These can be calculated using trig.

 

2) The motion of the projectile. Once you figure out where the projectile is actually being launched from (in terms of theta, the angle of the barrel from the ground), you will be able to set up a system of equations to solve this problem. You need to break the muzzle velocity into vector components. Use the components, the x displacement, and the y displacement to solve for theta.

 

I highly recommend that you draw a largish picture of the problem, so that you can fill in blanks as you figure them out.

[Cap'n Refsmmat]

I am guessing that the length of the cannon's barrel is to be ignored. That's the way all of the problems I have seen are.

 

You'll need to split the velocity into x and y components (even if you don't know the angle, fill in what you can) and plug those into the equations you do know. Eventually you'll know enough variables to solve for the angle.

 

Try it and tell us how far you get and we'll see if we can give you some more ideas.