Specific heat capacity (Calorimetry)

In summary, the conversation discusses the calculation of temperature rise in four steel brake disks when a car's kinetic energy is converted to internal energy through friction during braking. The equation c=Q/(m*dT) is used to calculate the change in temperature, with the assumption that all of the car's kinetic energy becomes heat. The final answer is 120 degrees Celsius.
  • #1
Lunar Guy
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0
[SOLVED] Specific heat capacity (Calorimetry)

Homework Statement


When a driver brakes an automobile, friction between the brake disks and the brake pads converts part of the car's translational kinetic energy to internal energy. If a 1500 kg automobile traveling at 32 m/s comes to a halt after its brakes are applied, how much can the temperature rise in each of the four 3.5 kg steel brake disks? Assume the disks are made of iron [tex](c_{p} = [/tex] 448 J/kg•°C) and that all of the kinetic energy is distributed in equal parts to the internal energy of the brakes.


Homework Equations



[tex]c_{p,x}m_{x}T_{x}[/tex] = [tex]c_{p,y} m_{y} T_{y}[/tex]




The Attempt at a Solution


I really don't know where to start with this problem... A little push and I can do the rest, but...

[tex]c_{p,x}m_{x}T_{x}[/tex] = [tex]c_{p,y} m_{y} T_{y}[/tex]
 
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  • #2
Bump. Can anyone help me out?
 
  • #3
Well that's not really the right equation involving specific heat you're looking at

You want the one that involves energy. You know the kinetic energy of the car from 1/2*mv^2, and it's given that all that energy becomes heat

A 4th of that goes into each 3.5kg brake, so do you have a formula that links specific heat, mass, temperature, and heat? (yes you do)
 
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  • #4
[tex]\Delta[/tex]PE + [tex]\Delta[/tex]KE + [tex]\Delta[/tex]U = 0?
 
  • #5
Well you could infer the equation from the units if you didn't know off hand(energy/mass*temp

c=Q/(m*dT) where dT is the change in temperature and Q is the amount of heat gained(which you find from assuming all the kinetic energy becomes heat)
 
  • #6
Thanks. I got it. It's 120 degrees Celsius, right?
 

Related to Specific heat capacity (Calorimetry)

1. What is specific heat capacity?

Specific heat capacity, also known as heat capacity, is the amount of heat energy required to raise the temperature of a substance by 1 degree Celsius per unit mass.

2. How is specific heat capacity measured?

Specific heat capacity is measured using a process called calorimetry. This involves measuring the temperature change of a known mass of a substance when a known amount of heat energy is added or removed.

3. What is the equation for specific heat capacity?

The equation for specific heat capacity is Q = mcΔT, where Q is the heat energy, m is the mass of the substance, c is the specific heat capacity, and ΔT is the change in temperature.

4. How does specific heat capacity differ between substances?

Specific heat capacity can vary greatly between different substances. This is because the ability of a substance to store heat energy depends on its molecular structure and composition.

5. How is specific heat capacity used in real life?

Specific heat capacity is used in various industries, such as cooking, heating and cooling systems, and in the production and transportation of food and other goods. It is also an important concept in thermodynamics and is used to calculate the efficiency of engines and other energy systems.

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