Trouble Finding Change in Temp Given KE = Q (Thermal Energy)

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SUMMARY

The discussion revolves around calculating the temperature increase of 100 kg of water when a 3 kg projectile traveling at 100 m/s is stopped in an insulated tank, converting its kinetic energy (KE) into thermal energy (TE). The kinetic energy is calculated as 15,000 J using the formula KE = 1/2 * mass * velocity². The thermal energy equation, TE = mass * specific heat * change in temperature, leads to a temperature change of approximately 0.0359 °C for the water. The participant expresses concern about the small temperature change and seeks validation of their calculations and logic.

PREREQUISITES
  • Understanding of kinetic energy calculations using KE = 1/2 * mass * velocity²
  • Knowledge of thermal energy calculations with TE = mass * specific heat * change in temperature
  • Familiarity with unit conversions, particularly between calories and joules
  • Basic principles of thermodynamics related to energy conservation
NEXT STEPS
  • Review the concept of energy conservation in thermodynamic systems
  • Learn about the heat capacity of different materials, including projectiles
  • Explore the implications of negligible temperature changes in thermal energy calculations
  • Investigate the effects of insulation on energy transfer in thermal systems
USEFUL FOR

Students in engineering and physics courses, particularly those focusing on thermodynamics and energy transfer, as well as anyone involved in practical applications of thermal energy calculations.

Oannes
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Homework Statement


A 3kg projectilce traveling at 100 m/s is stopped by being shot into an insulated tank containg 100kg of water. If the KE of the projectile is completely convereted into thermal energy, how much will the temp of the water increase in degrees celsius? The standard heat of water is 1 cal/g C.

Homework Equations


Thermal Energy = mass * Specific Heat * change in temperature
Kinetic Energy = 1/2 * mass * Velocity2
KE = TE

The Attempt at a Solution



So did all my conversions to get like units below.

1cal/g C = 4.18J/.001kg * C (Specific Heat of Water)

Then solved for Kinetic Energy:

KE = 1/2 (3kg) (100m/s)2
KE = 15000kg m2/s2 = 15000J

Then solved for Thermal Energy setting Kinetic equal to Thermal as it states in the problem:

15000J = 100kg (4.18J/.001kg C) * Change in Temp
15000J = 418000J/C * Change in Temp
.0359 C = Change in Temp


Now this seems to be my answer, and I think that maybe such a miniscule change could be my answer considering the circumstances, however I fear that I have done something wrong somewhere and cannot find it. Most of my problems so far have involved significant temperature change so I feel they are either changing things up or I have made a mistake somehwere. Is all my logic correct? or have I messed up somewhere? Also I understand this question could fall under physics, however they have us working this out in my Engineering and Problem Solving course. Thanks so much in advance.
 
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Oannes said:
Is all my logic correct?
The only "correction" that might be applied is to include the heat capacity of the projectile; it hasn't been specified, and could be argued to be < 4 mK , the uncertainty of the experiment, or, included if you feel that it is necessary.
 

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