How Hot Does a Bullet Get When Fired Into Wood?

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Homework Help Overview

The discussion revolves around the thermal effects of a .22 caliber bullet fired into wood, specifically focusing on the temperature rise of the bullet and whether it reaches a point where melting occurs. The problem involves concepts from thermodynamics and energy transfer, particularly kinetic energy and heat capacity.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss calculating the kinetic energy of the bullet and its conversion to heat. There are attempts to relate kinetic energy to temperature change using specific heat capacity. Some participants express confusion about unit conversions and the application of formulas.

Discussion Status

Several participants are actively engaging with the problem, sharing calculations and questioning the relationships between kinetic energy, heat transfer, and temperature rise. There is a recognition of the need to ensure correct unit usage and the relevance of specific heat capacity in the calculations. No consensus has been reached yet.

Contextual Notes

Participants note the importance of considering the specific heat capacity of lead and the melting point in their calculations. There is also mention of the potential for confusion due to unit conversions, particularly with mass and energy.

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Homework Statement



Ricky Plaxico Bobby grabs his .22 pistol and fires a 5.00g lead bullet into a block of wood. The muzzle Velocity 301 m/s. Assume that 50 % of the bullet turns to heat
A.What is the temperature rise of the bullet?
B. Will the bullet become hot enough to melt?
C.If so, what percent of the bullet melts?

Homework Equations


L=alphaL(subzero)T



The Attempt at a Solution


I converted the equation to get the temperature
L/alphaL(subzero)=T? i get a weird answer can i get some help? please
 
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First work out the kinetic energy of the bullet
then you need the specific heat capacity of lead to work out what temperature rise this energy corresponds to.
And finally the melting point of lead.

(Be careful of units, the bullet is given in grams )
 
i found the the kinetic energy its 752.5 and the melting point of the lead is 327 celsius and the specific heat is 130 kg c... i don't know how the kinetic energy plugs into this equation? I am using Q=mcT and to find Q i used this equation Q=mL, and then i pluged it into this one but i know its wrong because the answer i got was cold and its suppose to be hot?

(.005kg)(25kg= the heat fusion)=Q
.125kg

.125kg=(.005)(130)T
T=.1923076923 C?
 
All the kinetic energy becomes heat.
So Q = 1/2 m v2 and Q = m c T
Where T is the change in temperature - you just need to find if the temperature change is enough to reach lead's melting point
 

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