# Ballistics -- How deep does the bullet penetrate into the wood?

duchuy
Homework Statement:
How deep in a tree would a mass m firearm projectile penetrate at velocity v0 if the frictional force between the projectile and the wood is C ?
Relevant Equations:
d = mv^2 / 2C
Hi, I was given this exercice where I have to calculate the penetration distance, knowing that m = 20g, v = 300km/h and C = 750 N and I have to give the results with two significant numbers. I really thought that all I had to do was replace the values so I did :
d = (20.10^-3) x (300/3,6)^2 / 2x750 and I ended up with d = 0,0925925925...
But when I entered the answer with two significant figures = 0,093, the answer was wrong.
Sorry if i have misused any term, I translated this from french.

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Homework Statement:: How deep in a tree would a mass m firearm projectile penetrate at velocity v0 if the frictional force between the projectile and the wood is C ?
Relevant Equations:: d = mv^2 / 2C

Hi, I was given this exercice where I have to calculate the penetration distance, knowing that m = 20g, v = 300km/h and C = 750 N and I have to give the results with two significant numbers. I really thought that all I had to do was replace the values so I did :
d = (20.10^-3) x (300/3,6)^2 / 2x750 and I ended up with d = 0,0925925925...
But when I entered the answer with two significant figures = 0,093, the answer was wrong.
Sorry if i have misused any term, I translated this from french.
It looks right. It might be two decimal places, rather than two significant figures. Or, the answer in cm?

• duchuy
duchuy
oh my god the answer is actually in cm, thank you so much! how'd you figure that out...?

• berkeman
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