Physics Final Prep

A helium-filled weather balloon has a 0.90 m radius at liftoff where air pressure is 1.0 atm and the temperature is 298 K. When airborne, the temperature is 210 K, and its radius expands to 3.0 m. What is the pressure at the airborne location?

0\.019 atm

Evaporation cools the liquid that is left behind because the molecules that leave the liquid during evaporation:

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have greater than average speed.

If the temperature of an ideal gas contained in a box is increased:

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the average speed of the molecules in the box will be increased.

The ideal gas law treats gas as consisting of:

molecules

Boltzmann's constant, kB, may be derived as a function of R, the universal gas constant, and NA, Avogadro's number. Which expresses the value of kB?

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R/NA

What is the root-mean-square speed of chlorine gas molecules at a temperature of 320 K? (R = 8.31 J/mol•K, NA = 6.02 × 1023, and the molecular mass of Cl2 = 71)

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3\.4 × 102 m/s

The absolute temperature of an ideal gas is directly proportional to which of the following properties, when taken as an average, of the molecules of that gas?

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kinetic energy

An ideal gas is confined to a container with constant volume. The number of moles is constant. By what factor will the pressure change if the absolute temperature triples?

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3\.0

The internal energy of a monatomic ideal gas is equal to which of the following?

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(3/2)PV

Why do vapor bubbles get larger in boiling water as they approach the surface?

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The pressure in the water decreases as the bubble moves toward the surface.

How many atoms are present in a sample of pure iron with a mass of 300 g? (The atomic mass of iron = 56 and NA = 6.02 × 1023)

3\.2 × 10^24

A room has a volume of 60 m3 and is filled with air of an average molecular mass of 29 u. What is the mass of the air in the room at a pressure of 1.0 atm and temperature of 22°C? R = 0.082 L•atm/mol•K

72 kg

The average molecular kinetic energy of a gas can be determined by knowing only

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the temperature of the gas.

For an ideal gas of a given mass, if the pressure remains the same and the volume increases:

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the average kinetic energy of the molecules increases.

Metal lids on glass jars can often be loosened by running them under hot water. Why is this?

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The metal has a higher coefficient of thermal expansion than glass, so the metal expands more than the glass thus loosening the connection.

Phase changes occur

as the temperature remains the same.

The three phases of matter can exist together in equilibrium at the

triple point

The internal energy of an ideal gas depends on

its temperature.

When a solid melts

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heat energy enters the substance.

The absolute temperature of an ideal gas is directly proportional to which of the following?

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kinetic energy

A 5.0-cm diameter steel shaft has 0.10 mm clearance all around its bushing at 20°C. If the bushing temperature remains constant, at what temperature will the shaft begin to bind? Steel has a linear expansion coefficient of 12 × 10-6 /C°.

353°C

Which temperature scale never gives negative temperatures?

Kelvin

The temperature changes from 35°F during the night to 75°F during the day. What is the temperature change on the Celsius scale?

22 C°

The heat required to change a substance from the solid to the liquid state is referred to as the

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heat of fusion.

The reason ocean temperatures do not vary drastically is that

water has a relatively high specific heat.

Turning up the flame under a pan of boiling water causes

the water to boil away faster.

An aluminium rod 17.4 cm long at 20°C is heated to 100°C. What is its new length? Aluminium has a linear expansion coefficient of 25 × 10-6 /C°.

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17\.435 cm

The temperature of an ideal gas increases from 2°C to 4°C while remaining at constant pressure. What happens to the volume of the gas?

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It increases slightly.

The amount of heat necessary to raise the temperature of 1 gram of water by 1°C is referred to as the

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calorie

Convert 14°F to K.

263 K

Pressure is

proportional to force and inversely proportional to area.

Two Styrofoam balls, of radii R and 2R, are released simultaneously from a tall tower. Which will reach the ground first?

the larger one

A 500-N weight sits on the small piston of a hydraulic machine. The small piston has area 2.0 cm2. If the large piston has area 40 cm2, how much weight can the large piston support?

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10000 N

What is the gauge pressure if the absolute pressure is 300 kPa?

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199 kPa

A plastic block of dimensions 2.00 cm × 3.00 cm × 4.00 cm has a mass of 30.0 g. What is its density?

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1\.25 g/cm^3

A 50 cm3 of wood is floating on water, and 50 cm3 of iron is totally submerged. Which has the greater buoyant force on it?

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the iron

Which one of the following is associated with the law of conservation of energy in fluids?

Bernoulli's principle

A brick weighs 50.0 N, and measures 30.0 cm × 10.0 cm × 4.00 cm. What is the maximum pressure it can exert on a horizontal surface?

12\.5 kPa

A 200-N object floats with three-fourths of its volume beneath the surface of the water. What is the buoyant force on the object?

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200 N

Density is

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proportional to mass and inversely proportional to volume.

A 13,000 N vehicle is to be lifted by a 25 cm diameter hydraulic piston. What force needs to be applied to a 5.0 cm diameter piston to accomplish this?

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520 N

What is the difference between the pressures inside and outside a tire called?

gauge pressure

An object weighs 7.84 N when it is in air and 6.86 N when it is immersed in water. What is the specific gravity of the object?

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8\.0

An ideal fluid flows at 12 m/s in a horizontal pipe. If the pipe widens to twice its original radius, what is the flow speed in the wider section?

3\.0 m/s

An object floats with half its volume beneath the surface of the water. The weight of the displaced water is 2000 N. What is the weight of the object?

2000 N

Suppose a 0.3-kg mass on a spring that has been compressed 0.10 m has elastic potential energy of 1 J. What is the spring constant?

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200 N/m

When car shock absorbers wear out and lose their damping ability, what is the resulting oscillating behaviour?

underdamped

The bulk modulus of a material, as a meaningful physical property, is applicable to which of the following?

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solids, liquids, and gases

Three identical springs each have the same spring constant k. If these three springs are attached end to end forming a spring three times the length of one of the original springs, what will be the spring constant of the combination?

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k/3

Suppose a 0.3-kg mass on a spring that has been compressed 0.10 m has elastic potential energy of 1.0 J. How much further must the spring be compressed to triple the elastic potential energy?

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0\.07 m

Which one of the following quantities is at a maximum when an object in simple harmonic motion is at its maximum displacement?

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acceleration

A bridge piling has an area of 1.250 m2. It supports 1875 N. Find the stress on the column.

1500 N/m2

A simple pendulum has a period of 2.0 s. What is the pendulum length? (g = 9.8 m/s2)

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0\.99 m

A mass of 0.40 kg, hanging from a spring with a spring constant of 80 N/m, is set into an up-and-down simple harmonic motion. What is the speed of the mass when moving through the equilibrium point? The starting displacement from equilibrium is 0.10 m.

1\.4 m/s

Stress is

applied force per cross-sectional area.

At a depth of about 1030 m in the sea the pressure has increased by 100 atmospheres (to about 107 N/m2). By how much has 1.0 m3 of water been compressed by this pressure? The bulk modulus of water is 2.3 × 109 N/m2.

4\.3 × 10-3 m3

An aluminum wire 2.0 m in length and 2.0 mm in diameter supports a 10.0-kg mass. What is the elongation of the wire? (The Young's modulus for aluminum is 7.0 × 1010 N/m2)

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0\.89 mm

Strain is

the ratio of the change in length to the original length.

A sphere hanging freely from a cord is in

stable equilibrium.

A tire stops a car by use of friction. What modulus should we use to calculate the stress and strain on the tire?

shear modulus

The second hand of a clock has a length of 0.30 m. What distance does the tip of the second-hand sweep through in 3 minutes and 45 seconds?

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7\.1 m

What is the centripetal acceleration of a point on the perimeter of a bicycle wheel of diameter 70 cm when the bike is moving 8.0 m/s?

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1\.8 × 102 m/s2

A wheel of diameter 26 cm turns at 1500 rpm. How far will a point on the outer rim move in 2.0 s?

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41 m

How many rad/s is 25 revolutions per minute equivalent to?

2\.6 rad/s

What is the quantity used to measure an object's resistance to changes in rotation?

moment of inertia

A wheel accelerates with a constant angular acceleration of 4.5 rad/s2. If the initial angular velocity is 1.0 rad/s, what is the angle the wheel rotates through in 2.0 s?

11 rad

A wheel starts at rest and has an angular acceleration of 4 rad/s2. Through what angle does it turn in 3.0 s?

18 rad

Angular velocity is expressed in units of

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radians per second.

Consider a rigid body that is rotating. Which of the following is an accurate statement?

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All points on the body are moving with the same angular velocity.

A wheel of diameter of 68.0 cm slows down uniformly from 8.40 m/s to rest over a distance of 115 m. What is the angular acceleration?

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\-0.90 rad/s2

An ice skater performs a pirouette (a fast spin) by pulling in his outstretched arms close to his body. What happens to his rotational kinetic energy about the axis of rotation?

It increases.

If a constant net torque is applied to an object, that object will

rotate with constant angular acceleration.

Two equal forces are applied to a door. The first force is applied at the midpoint of the door; the second force is applied at the doorknob. Both forces are applied perpendicular to the door. Which force exerts the greater torque?

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the second at the doorknob

A solid cylinder of mass 10 kg is pivoted about a frictionless axis thought the center O. A rope wrapped around the outer radius R1 = 1.0 m, exerts a force F1 = 5.0 N to the right. A second rope wrapped around another section of radius R2 = 0.50 m exerts a force F2 = 6.0 N downward. How many radians does the cylinder rotate through in the first 5.0 seconds, if it starts from rest?

5\.0 rad

"The total angular momentum of a system of particles changes when a net external force acts on the system." This statement is

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sometimes true. It depends on the force's point of application.

A 4.00-kg mass sits at the origin, and a 10.0-kg mass sits at x = + 21.0 m. Where is the center of mass on the x-axis

\+15.0 m

What is the momentum of a 2000-kg truck traveling at 35 m/s?

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7\.0 × 104 kg.m/s

In a game of pool, the white cue ball hits the #5 ball and stops, while the #5 ball moves away with the same velocity as the cue ball had originally. The type of collision is

elastic

A 4.0-N force acts for 3.0 s on an object. The force suddenly increases to 15 N and acts for one more second. What impulse was imparted by these forces to the object?

27 N.s

Which of the following is a false statement?

__**a. The center of mass of an object must lie within the object.**__

b. The center of gravity of an object may be thought of as the "balance point."

c. For an object on the surface of the Earth, the center of gravity and the center of mass are the same point.

d. For a uniform symmetric object, the center of mass is at the center of symmetry.

When a cannon fires a cannonball, the cannon will recoil backward because the

momentum of the cannonball and cannon is conserved.

A red ball with a velocity of +3.0 m/s collides head-on with a yellow ball of equal mass moving with a velocity of -2.0 m/s. What is the velocity of the yellow ball after the collision?

\+3.0 m/s

Two objects collide and bounce off each other. Linear momentum

is definitely conserved.

Two objects collide and stick together. Kinetic energy

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is definitely not conserved.

A rubber ball and a lump of putty have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same speed with which it hit. The putty sticks to the wall. Which objects experiences the greater momentum change?

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the ball

Which of the following is an accurate statement?

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a. The momentum of a moving object is constant.

b. __**If an object is acted on by a non-zero net external force, its momentum will not remain constant.**__

c. If the kinetic energy of an object is doubled, its momentum will also double.

d. The momentum of a projectile is constant.

A 1000-kg car traveling at 25 m/s runs into the rear of a stopped car that has a mass of 1500 kg and they stick together. What is the speed of the cars after the collision?

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10 m/s

A 3.0-kg object moves to the right at 4.0 m/s. It collides head-on with a 6.0-kg object moving to the left at 2.0 m/s. Which statement is correct?

The total momentum both before and after the collision is zero.

A handball of mass 0.10 kg, traveling horizontally at 30 m/s, strikes a wall and rebounds at 24 m/s. What is the change in the momentum of the ball?

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5\.4 kg.m/s

A 3.0-kg object moves to the right at 4.0 m/s. It collides in a perfectly inelastic collision with a 6.0 kg object moving to the left at 2.0 m/s. What is the total kinetic energy after the collision?

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0 J

A horizontal force of 200 N is applied to move a 55-kg cart (initially at rest) across a 10 m level surface. What is the final speed of the cart?

8\.5 m/s

You lift a 10-N physics book up in the air a distance of 1.0 m, at a constant velocity of 0.50 m/s. What is the work done by the weight of the book?

\-10 J

The quantity 1/2 mv2 is

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the kinetic energy of the object.

A cyclist does work at the rate of 500 W while riding. How much force does her foot push with when she is traveling at 8.0 m/s?

63 N

A 100-N force has a horizontal component of 80 N and a vertical component of 60 N. The force is applied to a box which rests on a level frictionless floor. The cart starts from rest and moves 2.0 m horizontally along the floor. What is the cart's final kinetic energy?

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160 J

An object is lifted vertically 2.0 m and held there. If the object weighs 90 N, how much work was done in lifting it?

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180 J

A 10-N force is needed to move an object with a constant velocity of 5.0 m/s. What power must be delivered to the object by the force?

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50 W

What is the correct unit of work expressed in SI units?

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kg m2/s2

A container of water is lifted vertically 3.0 m then returned to its original position. If the total weight is 30 N, how much work was done?

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No work was done

The total mechanical energy of a system

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is constant, only if conservative forces act.