5-8 ODDS

Question 1

Give two examples of a fluid.

Answer 1

Liquid and gas because they both flow.

Question 2

Distinguish between mass density and weight density.

Answer 2

Mass density is mass per volume; weight density is weight per volume.

Question 3

How does the pressure exerted by a liquid change with the depth in the liquid? How does the pressure exerted by a liquid change as the density of the liquid changes?

Answer 3

According to the formula liquid pressure = density x depth, pressure increases with an increase in depth and pressure increases with an increase in density.

Question 4

How does the water pressure 1 m below the surface of a small pond compare to water pressure 1 m below the surface of a huge lake?

Answer 4

Pressure at the same depth is the same in both the pond and the lake.

Question 5

Why does buoyant force act upward on an object submerged in water?

Answer 5

The buoyant force acts upward because pressure is greater against the bottom where the water is deeper.

Question 6

State Archimedes’ principle.

Answer 6

An immersed body is buoyed up by a force equal to the weight of fluid displaced.

Question 7

How does the buoyant force on a fully submerged object compare with the weight of the water displaced?

Answer 7

The buoyant force is equal to the weight of the water displaced.

Question 8

If a 1-L container is immersed halfway in water, what is the volume of the water displaced? What is the buoyant force on the container?

Answer 8

The volume of water displaced is 0.5L, and the buoyant force is 4.9N.

Question 9

What weight of water is displaced by a 100-ton floating ship? What is the buoyant force that acts on this ship?

Answer 9

Since 100 tons of water are displaced by a 100-ton floating ship, the buoyant force on the ship is 100 tons.

Question 10

What happens to the air pressure inside a balloon when the balloon is squeezed to half its volume at constant temperature?

Answer 10

The pressure is double when the balloon is squeezes to half its volume.

Question 11

How does the downward pressure of the 76-cm column of mercury in a barometer compare with the air pressure at the bottom of the atmosphere?

Answer 11

Both pressures are the same.

Question 12

Why would a water barometer have to be 13.6 times as tall as a mercury barometer?

Answer 12

Because the density of water is 1/13.6 that of mercury, a water column needs to be 13.6 times taller than a mercury column to have the same weight and produce the same pressure.

Question 13

What happens to the pressure in all parts of a confined fluid when the pressure in one part is increased?

Answer 13

An increased in pressure in one part of a confined fluid is transmitted throughout the fluid to all parts.

Question 14

A balloon that weights 1 N is suspended in air, drifting neither up nor down. How much buoyant force acts on it? What happens if the buoyant force decreases? Increases?

Answer 14

When the balloon is in equilibrium, its buoyant force equals its weight, 1 N. If the buoyant force decreases, it will move downward; if it increases, the balloon will rise.

Question 15

Does Bernoulli’s principle refer to internal pressure changes in a fluid, or to pressures that a fluid can exert on objects in the path of the flowing fluid? Or Both?

Answer 15

Bernoulli’s principle refers only to the internal pressure changes in a fluid.

Question 16

What are the temperatures for freezing water on the Celsius and Farenheit scales? For boiling water?

Answer 16

Water freezes at 0 DEGREE C and 32 DEGREES F, and boils at 100 DEGREES C and 212 DEGREES F.

Question 17

Under what conditions can we say that a “thermometer measures its own temperature?”

Answer 17

The necessary condition is thermal equilibrium because only then do the thermometer and thing being measured have the same temperature.

Question 18

What pressure would you expect in a rigid container of 0oC gas if you cooled it to -273oC?

Answer 18

The pressure would be zero at -273oC.

Question 19

How much energy can be removed from a system at 0 K?

Answer 19

No energy can be removed from a system at 0 K.

Question 20

Does a hot object contain thermal energy, or does it contain heat?

Answer 20

Hot objects contain thermal energy, not heat.

Question 21

What role does temperature play in the direction of thermal energy flow?

Answer 21

The direction of thermal energy flow is from objects at higher temperatures to objects at lower temperatures.

Question 22

How many joules are needed to change the temperature of 1 g of water by 1oC?

Answer 22

The energy is 4.19 J.

Question 23

Distinguish among a calorie, a Calorie, and a joule.

Answer 23

ALL are units of energy.

Question 24

What happens to heat added to a system that doesn’t increase the temperature of the system?

Answer 24

Added heat that doesn’t raise the temperature increases the thermal energy of the system and/or does external work if it leaves the system.

Question 25

When can thermal energy in a system move from lower to higher temperatures?

Answer 25

Thermal energy can move from lower to higher temperatures only when external work is done on the system.

Question 26

When disorder in a system increases, does entropy increase or decrease?

Answer 26

Entropy is a measure of disorder. The greater the disorder, the greater the entropy.

Question 27

Which warms faster when heat is applied: iron or silver? Which has the higher specific heat capacity?

Answer 27

Silver heats more quickly and has the higher specific heat.

Question 28

What is the relationship between water’s high specific heat capacity and the climate of Europe?

Answer 28

Thermal energy is carried in the Gulf Stream from tropical waters to the North Atlantic, where it warms the otherwise cold climate.

Question 29

Which generally expands more for an equal increase in temperature: solids or liquids?

Answer 29

Liquids generally expand more for an equal increase in temperature.

Question 30

What is the reason ice is less dense than water?

Answer 30

Ice is less dense than water due to its ice crystals that have open structures.

Question 31

What are the three common ways in which heat is transferred?

Answer 31

Conduction, convection, and radiation.

Question 32

How is a barefoot fire walker able to walk safely on red-hot wooden coals?

Answer 32

Wood is a good insulator even when it’s red hot.

Question 33

By what means is heat transferred by convection?

Answer 33

Heat is transferred by the movement of fluids.

Question 34

Why isn’t Millie’s hand burned when she holds it above the escape valve of the pressure cooker?

Answer 34

A: Her hand is not in steam, but in a jet of condensed vapor that has expanded and cooled.

Question 35

How does the peak frequency of radiant energy relate to the absolute temperature of the radiating source?

Answer 35

Peak frequency and absolute temperature are directly proportional: f ~ T.

Question 36

Because all objects emit energy to their surroundings, why don’t the temperatures of all objects continuously decrease?

Answer 36

Temperatures don’t continuously decrease because all objects are absorbing radian energy.

Question 37

Which undergoes a faster rate of cooling: a red-hot poker in a warm oven or a red-hot poker in a cold room? (Or do both cool at the same rate?)

Answer 37

By Newton’s law of cooling, the hot poker in the cold room radiates more because of the greater temperature difference between the poker and the room.

Question 38

What would be the consequence to Earth’s climate if the greenhouse effect were completely eliminated?

Answer 38

Without the greenhouse effect, Earth would be a very cold place, with an average temperature about -18 DEGREES C.

Question 39

What are the four common phases of matter?

Answer 39

The four common phases of matter are solids, liquids, gases, and plasmas.

Question 40

What is evaporation, and why is it a cooling process?

Answer 40

Evaporation is the change of phase from liquid to gas. As fast-moving molecules in a liquid escape into the air, slower ones on average are left behind, thereby cooling the water.

Question 41

What is condensation, how does it differ from evaporation, and why is it a warming process?

Answer 41

Condensation is the opposite of evaporation. Gas molecules near the surface of a liquid are attracted to the liquid, strike it with increased KE, and thereby warm the liquid.

Question 42

Distinguish between evaporation and boiling.

Answer 42

Evaporation is a phase change at the surface of a liquid; boiling is a phase change that occurs throughout a liquid, producing bubbles.

Question 43

Is it the boiling of the water or the higher temperature of the water that cooks food faster in a pressure cooker?

Answer 43

High temperature cooks food, not the bubbles associated with boiling.

Question 44

Why does decreasing temperature of a liquid make it freeze?

Answer 44

Molecular motion slows, thus allowing molecules to bind together.

Question 45

Does a liquid release energy or absorb energy when it changes into a gas? When it changes into a solid?

Answer 45

A liquid absorbs energy when it changes into a gas; when a liquid changes into a solid, it gives off energy.

Question 46

Which part of an atom is positively charged, and which part is negatively charged?

Answer 46

The nucleus and its protons are positively charged; electrons are negatively charged.

Question 47

How do the masses of electrons compare with the masses of protons?

Answer 47

The masses of electrons are much less than the masses of protons.

Question 48

What kind of charge does an object acquire when electrons are stripped from it?

Answer 48

When electrons are stripped from an object, it is left with a positive charge.

Question 49

How is Coulomb’s law similar to Newton’s law of gravitation? How is it different?

Answer 49

Both laws are inverse-square laws. How they differ is mainly that gravitation is only attractive, whereas electrical forces can repel.

Question 50

How does the magnitude of electrical force between a pair of charged particles change when the particles are moved twice as far apart? Three times as far apart?

Answer 50

By the inverse-square law, particles twice as far apart have 1/9 the force.

Question 51

Give two examples of common force fields.

Answer 51

Two force fields are gravitational and electric.

Question 52

Distinguish between electrical potential energy and electric potential in terms of units of measurement.

Answer 52

Electric potential energy is measured in joules; electric potential in volts.

Question 53

What condition is necessary for a sustained flow of electric charge through a conducting medium?

Answer 53

A sustained flow needs a sustained difference in potential across a conducting medium, such as a battery or generator.

Question 54

Does electric charge flow across a circuit or through a circuit? Does voltage flow across a circuit or is it impressed across a circuit?

Answer 54

Electric charge flows through a circuit. Voltage doesn’t flow at all but is impressed across a circuit.

Question 55

Does a battery produce dc or ac? Does the generator at a power station produce dc or ac?

Answer 55

A battery produces dc. A generator normally produces ac.

Question 56

What is the unit of electrical resistance?

Answer 56

The unit of electrical resistance is the ohm, symbol Ω.

Question 57

Which has greater electrical resistance: wet skin or dry skin?

Answer 57

Dry skin has considerably more electrical resistance than wet skin.

Question 58

What is the source of electrons that produces a shock when you touch a charged conductor?

Answer 58

The source of electrons producing a shock is your own body.

Question 59

As more lines are opened at a fast-food restaurant, the resistance to the motion of people trying to get served is reduced. How is this similar to what happens when more branches are added to a parallel circuit?

Answer 59

The more branches in both cases, the less the overall resistance.