Solving for Impact Velocity: A Bullet of Ice at 0°C

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SUMMARY

The discussion focuses on calculating the impact velocity required for a bullet of ice at 0°C to melt 68% of its mass upon impact. Participants utilize the kinetic energy formula (1/2mv²) and the heat energy equation (Q = ml) to derive the necessary velocity. The correct approach involves equating the kinetic energy to the energy required to melt 0.68m of ice, leading to the conclusion that the impact velocity must be approximately 674 m/s. This calculation is essential for understanding energy transfer in phase changes during impacts.

PREREQUISITES
  • Understanding of kinetic energy (1/2mv²)
  • Knowledge of heat energy and phase changes (Q = ml)
  • Basic algebra for solving equations
  • Familiarity with the properties of ice and its melting point
NEXT STEPS
  • Study the relationship between kinetic energy and phase change in materials
  • Learn about energy conservation principles in physics
  • Explore the specific heat capacity of ice and water
  • Investigate real-world applications of impact physics in materials science
USEFUL FOR

Students in physics, engineers working with materials under impact conditions, and anyone interested in thermodynamics and energy transfer principles.

noobatphysics
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Homework Statement


A Bullet of ice at a temperature of 0 degrees celieus is fired into a target
Assuming that all the impact energy is retained by the ice
what impact velocity is needed to melt 68% of the ice

Homework Equations



1/2mv^2
Q = ml

The Attempt at a Solution


i got..
v^2 = 668000
i doubt that is the correct answer
can some show me the steps to work this out
 
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Why didn't you use the 68%? The kinetic energy turns into the energy needed to melt 0.68m, not m.
 
um I am still puzzled
LOL
can u show me the steps?
 
I thought you used:

1/2mv^2
Q = ml

and equated them to get:

1/2mv^2=ml
v^2=2l

The statement 1/2mv^2=ml means "all the kinetic energy turns into the energy needed to melt the mass". However, only 68% of the mass melts, so the kinetic energy has to equal 0.68ml.
 
oh i see...

i got... 674 m/sec

doesn't seem right

Ek = 334800 x .68?
 

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