Bennett Mechanical Thermodynamics and Heat Questions and Answers

Question 1

A bimetallic strip is constructed by bonding a strip of steel to a strip of copper.
Copper has a higher coefficient of thermal expansion than steel.
If the straight strip is uniformly heated, how will it respond?

Accepted Answer

It will bend with the steel on the inside (concave side) of the curve.

Answer

It will remain straight but will become slightly thicker.

Answer

It will bend with the copper on the inside (concave side) of the curve.

Answer

It will twist into a corkscrew shape.

Question 2

To most effectively heat a room using natural air circulation, where should a hot air vent be placed?

Accepted Answer

Low on a wall, near the floor.

Answer

In the center of the ceiling, blowing downwards.

Answer

High on an interior wall.

Answer

In the exact center of the room on the floor.

Question 3

A person stands at an equal distance from four large, flat plates, all heated to the same high temperature. Which plate will radiate the most heat to the person?

Accepted Answer

A rough, matte black plate.

Answer

A shiny, polished silver plate.

Answer

A smooth, white-painted plate.

Answer

A clear glass plate.

Question 4

On a day when the room temperature is 70°F (21°C), why does a metal doorknob feel colder to the touch than a wooden door?

Accepted Answer

The metal has a higher rate of thermal conductivity.

Answer

The metal is actually at a lower temperature than the wood.

Answer

The wood retains latent heat better than the metal.

Answer

The metal has a smoother surface, increasing contact area.

Question 5

Sweating cools the body down on a hot day. This cooling effect is primarily a result of:

Accepted Answer

The evaporation of sweat, which requires energy taken from the skin.

Answer

The high specific heat of water absorbing ambient heat.

Answer

Conductive heat transfer from the moving air to the sweat.

Answer

The temperature of the sweat being lower than the body's temperature.

Question 6

A vacuum flask (thermos) keeps liquids hot by minimizing heat transfer. The vacuum between the inner and outer walls is MOST effective at preventing which forms of heat transfer?

Accepted Answer

Conduction and Convection

Answer

Radiation and Conduction

Answer

Convection and Radiation

Answer

Evaporation and Conduction

A bimetallic strip is constructed by bonding a strip of steel to a strip of copper.Copper has a higher coefficient of thermal expansion than steel.If the straight strip is uniformly heated, how will it respond?

A bimetallic strip is constructed by bonding a strip of steel to a strip of copper.
Copper has a higher coefficient of thermal expansion than steel.
If the straight strip is uniformly heated, how will it respond?