How Does Friction Affect Temperature Change in a Sliding Crate?

In summary, the crate of fruit slides down an incline and friction causes work to be done on it. The work is negative, so the fruit warms up.
  • #1
WY
28
0
hey I'm wondering if someone can help un-stuck me on this question - I'm not sure if what I'm diong is right ><

A crate of fruit with a mass of 31.0kg and a specific heat capacity of 3800 J/kg K slides down a ramp inclined at an angle of 38.4 below the horizontal. The ramp has a length of 9.00 m.

I got the first part of the question which was:
If the crate was at rest at the top of the incline and has a speed of 2.20 m/s at the bottom, how much work W_f was done on the crate by friction?

and then the next part is:
f an amount of heat equal to the magnitude of the work done by friction goes into the crate of fruit and the fruit reaches a uniform final temperature, what is its temperature change DeltaT?

so i went ahead and did it using Q=mcdeltaT with Q = W_f and m= 31 and c= 3800 to work out delta T or should m = mgsin38.4? I can't seem to figure what mass I need to use!

Thanks in advance :smile:
 
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  • #2
All of the fruit is being warmed up by absorbing the heat generated, so m is what you need. m = mgsin38.4 does not make sense for a couple of reasons. First, it is dimensionally incorrect. The left side is mass and the right side is force. Second, mass is a scalar quantitiy; it does not have direction associated with it, so it does not have components in different directions the way vectors do. There may be reasons to divide mass into parts in some problems (not this one), but that division will not involve direction angles.
 
  • #3
Hey that does make sense thanks!
But when I tried doing that -since i got W_f=-1630
I would calculate that -1630 = 31x3800xdeltaT
which would be -0.0138 - but this is wrong - have i missed out using a formula? or substituted in the wrong numbers?
 
  • #4
Apart from the minus sign (heat is added to the crate so [itex]\Delta Q][/itex] is positive) it looks all right to me. Don't know why it would be wrong...
 

1. What is heat transfer and friction?

Heat transfer is the movement of thermal energy from one object to another. Friction is the resistance encountered when two objects move against each other.

2. How does heat transfer occur?

Heat transfer can occur through three methods: conduction, convection, and radiation. Conduction is the transfer of heat through direct contact between two objects. Convection is the transfer of heat through the movement of fluids or gases. Radiation is the transfer of heat through electromagnetic waves.

3. What factors affect heat transfer?

The rate of heat transfer is affected by the temperature difference between two objects, the surface area of the objects, and the type of material the objects are made of. Other factors such as the presence of insulation, air flow, and surface texture can also affect heat transfer.

4. How does friction affect heat transfer?

Friction can generate heat, known as frictional heat, when two surfaces rub against each other. This can result in an increase in temperature and affect the rate of heat transfer between the two surfaces.

5. How is heat transfer and friction used in everyday life?

Heat transfer and friction are important concepts in many aspects of our daily lives. They are used in cooking, transportation, and energy production. For example, the friction between car tires and the road helps to generate heat, which allows the car to move forward. In cooking, heat transfer is used to cook food by transferring heat from a heat source to the food. In energy production, friction is used to convert mechanical energy into heat energy, which can then be converted into electricity.

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