Question

1. A commonly used packing material consists of “bubbles” of air trapped between bonded layers of plastic. Why does this packing material offers less protection on cold days than on warm days? Hint: Use the ideal gas law.

2. A tightly sealed house has a large ceiling fan that blows air out of the house and into the attic. If the fan is turned on, and the windows or doors to the house are left closed, what happens to the air pressure in the house after the fan has been on for a while?

Answer 1

1)

As air is trapped in the bubbles, volume of gas and molecules is fixed. The pressure exerted by the bubbles is a function of temperature.

As per ideal gas law

PV = nRT

In is very obvious that Temperature is less on colder days than on warmer days, therefore, on colder days, the pressure of the air in the bubbles is less and hence magnitude of the normal force on a packed object is smaller. Therefore, the packing material offers less protection on cold days.

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2)

As all the doors and windows are closed, volume will not change. As per PV = nRT, If the temperature of the air inside the house remains constant, the pressure in the house will decrease because fan is blowing molecules ( n ) out of the house.