What Is the Net Force on Each Side of a Heated Sealed Box?

But it's not really clear whether you are supposed to assume that.In summary, the problem involves a cubic metal box with sides of length 20cm that contains air at a pressure of 1 atm and a temperature of 300K. The box is then heated to 400K while maintaining a constant volume. The net force on each side of the box can be calculated using the equation PV=nRT and is found to be 8106 N. However, it is unclear if the problem assumes the box is in air at atmospheric pressure or not.
  • #1
jin
8
0
thermal expansion?

I need help asap! the question goes like this...

A cubic metal ox with sides of length 20cm contains air at pressure of 1 atm and a temperature of 300K. the box is sealed so that the volume is constant and heated to 400K. what is the net force on each side of the box? :confused:
 
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  • #2
PV = nRT --> P/T = nR/V = const.
P0= 1 atm T0=300k
P1= P0*T1/T0 = 4/3 atm = 135100 Pa
F= (P1 - Patm)* S = (135100 Pa - 101325 Pa)* (0.2m^2 * 6) = 8106 N

Bye Final
 
  • #3
jin said:
what is the net force on each side of the box?
Well, I presume the net force on each side is zero! :smile:

But I suppose they want you to find the outward force on each side of the box due to the pressure of the enclosed air.

If you can assume that this box is itself in air at atmospheric pressure, then you can find the net force due to air pressure by subtracting the outside air pressure, like Final did.
 

1. What is thermal expansion?

Thermal expansion is the tendency of matter to expand in volume when heated. This is due to the increase in molecular motion and the resulting increase in space between molecules.

2. What are the factors that affect thermal expansion?

The three main factors that affect thermal expansion are temperature, material composition, and the initial size or shape of the object. Generally, materials with more free space between molecules will expand more when heated.

3. How is thermal expansion measured?

Thermal expansion is typically measured by the coefficient of thermal expansion (CTE). This is the change in length or volume per unit change in temperature. It is expressed in units of length per unit of temperature (e.g. mm/°C).

4. Why is thermal expansion important?

Thermal expansion is important in many areas of science and engineering. It can cause structures to expand and contract, leading to potential damage or failure. It is also used in applications such as thermometers, thermostats, and bimetallic strips.

5. How can I prevent thermal expansion from causing damage?

To prevent damage from thermal expansion, engineers and scientists use different materials with different coefficients of thermal expansion, or they may use materials with high thermal conductivity to distribute the heat evenly and reduce the effects of expansion. Additionally, proper design and construction techniques can also help minimize the effects of thermal expansion.

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