EP 201 Exam 2 study guide

work input = work output

(Fd) = (Fd)

the pascal is a pressure unit equal to 1 kg per square meter 1 kg per square centimeter 1 N per square centimeter 1 N per square meter

1 N per square meter

What is the volume of a sugar cube that measures 1 cm on each side? What is the cross-sectional area of the cube? The total surface area? 1 cm3, 1 cm2, 1 cm2 1 cm3, 1 cm2, 6 cm2 1 cm3, 2 cm2, 4 cm2 1 cm3, 2 cm2, 6 cm2

1 cm3, 1 cm2, 6 cm2

What will the kinetic energy of a pile driver ram be if it starts from rest and undergoes a 10 kJ decrease in potential energy? 0 kJ 10 kJ -10 kJ 5 kJ

10 KJ

the power expended doing 100 J of work in 50 s is 2 W 50 W 1/2 W 4 W 5000 W

2 W

If you push a crate horizontally with 100 N across a 10-m factory floor and the friction between the crate and the floor is a steady 70 N, how much kinetic energy does the crate gain? -400 J -300 J -1000 J -700 J

300 J

When the useful energy output of a simple machine is 100 J, and the total energy input is 200 J, the efficiency is _______. 50 %. 200 % 100 %. 75 %.

50%

If the pressure in a hydraulic press is increased by an additional 10 N/cm2, how much extra load will the output piston support if its cross-sectional area is 50 cm2? 50 N 5N 1/5 N 500 N

500 N

If an input of 100 J in a pulley system increases the potential energy of a load by 60 J, what is the efficiency of the system? 60% 40% 100% 0%

60%

How is the density of a fish controlled? How is the density of a submarine controlled? A fish changes its volume, and a submarine changes its volume, too. A fish changes its volume, whereas a submarine changes its weight. A fish changes its weight, whereas a submarine changes its volume. A fish changes its weight, whereas a submarine changes its mass.

A fish changes its volume, whereas a submarine changes its weight.

Distinguish between tension and compression. A pulled-apart object is in tension; a pushed-together one is in compression. A high-density object is under tension; a low-density one is under compression. Tension causes things to get shorter and wider; compression causes things to get longer and thinner. In tension, atoms are closer together; in compression, they are further apart.

A pulled-apart object is in tension; a pushed-together one is in compression.

Why doesn't the Leaning Tower of Pisa topple over? A vertical line through the center of gravity passes through the center of its support base. The center of gravity is suspended below its support base. The center of gravity is at the center of the building. A vertical line through the center of gravity passes inside its support base.

A vertical line through the center of gravity passes inside its support base.

Distinguish between linear momentum and angular momentum. Angular momentum depends on the distribution of mass, whereas linear momentum depends on the total mass. Angular momentum depends on the total mass, whereas linear momentum depends on the distribution of mass. Angular momentum depends on tangential velocity, whereas linear momentum depends on the rotational velocity. Angular momentum depends on the distribution of mass times the total mass, whereas linear momentum depends only on the distribution of mass.

Angular momentum depends on the distribution of mass, whereas linear momentum depends on the total mass.

How does the arrangement of atoms in a crystalline substance differ from the arrangement in a noncrystalline (amorphous) substance? Hints -Atoms in crystals are located in a cubic array. In amorphous materials, they are hexagonal. -Atoms in crystals are in an ordered array. In amorphous materials, they are randomly distributed. -Atoms in amorphous materials are in an ordered array. In crystals, they are randomly distributed. -Atoms in crystals are closer together than atoms in amorphous materials.

Atoms in crystals are in an ordered array. In amorphous materials, they are randomly distributed.

What happens to the volume of a loaf of bread that is squeezed? The mass? The density? -Decreases, stays the same, increases -Increases, stays the same, decreases -Increases, decreases, stays the same -Stays the same, increases, decreases

Decreases, stays the same, increases

Select the correct equations that show that a machine that has an input of 100 J and an output of 35 J is 35 % efficient. Efficiency η=(Ein/Eout)2⋅100%=((100J)/(35J))2⋅100%=35% Efficiency η=(Eout/Ein)⋅100%=((35J)/(100J))⋅100%=35% Efficiency η=(Eout/Ein)2⋅100%=((35J)/(100J))2⋅100%=35% Efficiency η=(Ein/Eout)⋅100%=((100J)/(35J))⋅100%=35%

Efficiency η=(Eout/Ein)⋅100%=((35J)/(100J))⋅100%=35%

Calculate the tension in a horizontal string that whirls a 2.0-kg toy in a circle of radius 2.0 m when it moves at 2.5 m/s on an icy surface. centripetal force: F=mv^2 / r

F = 6.3 N

Why isn't there a horizontal buoyant force on a submerged object? Force vectors on the sides cancel one another. Forces on the top and bottom add and cancel gravity. Forces on the sides are zero at every point. Force vectors on the top and bottom cancel one another.

Force vectors on the sides cancel one another.

Is the buoyant force on a submerged object equal to the weight of the object itself or is it equal to the weight of the fluid displaced by the object? It is equal to the weight of the fluid displaced. It is equal to both the weight of the object and the weight of the fluid displaced. It is equal to the weight of the object. Neither. It is equal to the mass of the fluid displaced.

It is equal to the weight of the fluid displaced.

Suppose our experimenter repeats his experiment on a planet more massive than Earth, where the acceleration due to gravity is g=30 m/s2. When he releases the ball from chin height without giving it a push, how will the ball's behavior differ from its behavior on Earth? Ignore friction and air resistance. (Select all that apply.) -It will stop well short of his face. -It will take more time to return to the point from which it was released. Its mass will be greater. -It will take less time to return to the point from which it was released. -It will smash his face.

It will take less time to return to the point from which it was released.

How much work is done when you push a crate horizontally with 150 N across a 10-m factory floor? .If the force of friction on the crate is a steady 70 N, find the KE gained by the crate.

K = 800 J

Belly-flop Bernie dives from atop a tall flagpole into a swimming pool below. His potential energy at the top is 14000 J (relative to the surface of the pool). What is his kinetic energy when his potential energy reduces to 1000 J?

KE = 1.3×104 J

Calculate the kinetic energy of an 88-kg scooter moving at 18 m/s .

KE = 1.4×104 J

kinetic energy E

KE = 1/2 mv^2

A person having a mass of 55 kg sits on the edge of a horizontal rotating platform, 2.3 m from the center of the platform, and has a tangential speed of 6.4 m/s. Calculate the angular momentum of the person. angular momentum = mvr

L = 810 kg⋅m2/s

How is a flywheel constructed to maximize its rotational inertia? -Most of the mass is concentrated near a ring half way between the axis and the rim. -Most of the mass is concentrated near the axis. -The mass is uniformly distributed across the radius of the disk. -Most of the mass is concentrated far from the axis.

Most of the mass is concentrated far from the axis.

Can a force produce a torque when there is no lever arm? yes no

NOOOOOOO

power E

P=work done / time interval

Is pressure greater or less in regions where streamlines are crowded? Pressure is higher where streamlines are closer. Pressure is greater near the top streamlines and lower near the bottom, regardless of spacing. Pressure is lower where streamlines are closer. Pressure does not depend on streamline spacing.

Pressure is lower where streamlines are closer.

If the world's populations moved to the North Pole and the South Pole, would the 24-hour day become longer, shorter, or stay the same? longer shorter stay the same

ShoRtEr

What is Hooke's law? Does it apply to elastic materials or to inelastic materials? Stretch is proportional to force for elastic and inelastic materials. Stretch is inversely proportional to force for elastic materials. Stretch is proportional to force for elastic materials. Stretch is proportional to force for inelastic materials.

Stretch is proportional to force for elastic materials

Why are high-altitude research balloons only partially inflated when launched? Helium gas has become very expensive, so the smallest amount possible is used. The balloon is partially filled to give it a teardrop shape, so it will rise rapidly with less air resistance. The atmospheric pressure increases as they rise, so they expand, causing them to rise rapidly. The atmospheric pressure decreases as they rise, so they expand. If they were fully inflated at launch, they would burst at high altitudes.

The atmospheric pressure decreases as they rise, so they expand. If they were fully inflated at launch, they would burst at high altitudes.

Where is the center of mass of a baseball? Where is its center of gravity? The center of mass is at the center of the spherical ball, whereas the center of gravity is 1 mm above that. The center of mass is 1 mm above the center of the spherical ball, whereas the center of gravity is 1 mm below. The center of mass is at the center of the spherical ball, whereas the center of gravity is 1 mm below that. The center of mass and the center of gravity are both at the center of the spherical ball.

The center of mass and the center of gravity are both at the center of the spherical ball.

How does faster-moving air above an airplane wing affect the pressure on the wing? Faster airflow does not change the pressure over the wing - it remains at atmospheric pressure. High-speed air creates higher air pressure over the wing. High-speed air creates lower pressure over the wing only as it slows down after passing the high point of the wing. The speed increases as the air flows over the wing, so the pressure decreases.

The speed increases as the air flows over the wing, so the pressure decreases.

If you are not wearing a seat belt in a car that rounds a curve, and you slide across your seat and slam against a car door, what kind of force is responsible for your slide: centripetal, centrifugal, or no force? There is no force as viewed by someone outside the car. To them you move in a straight line. It is centripetal force, but only as viewed by someone inside the car. Centripetal force It is centrifugal force as viewed by someone outside the car.

There is no force as viewed by someone outside the car. To them you move in a straight line.

How much work is done when you push a crate horizontally with 150 N across a 10-m factory floor?

W = 1500 J

Select the correct equations that show that 9.6 J of work is done when a force of 8.0 N moves a book 1.2 m. W=F/d=(8.0N)/(1.2m)=9.6J W=F/d=(8.0N)/(1.2s)=9.6J W=F⋅d=(8.0N)⋅(1.2m)=9.6J W=F⋅d=(8.0N)⋅(1.2s)=9.6J

W=F⋅d=(8.0N)⋅(1.2m)=9.6J

How does the height to which water is lifted in a capillary tube relate to adhesion and the weight of the water lifted? Water rises to a height where the adhesive forces equal the weight of the water lifted. Adhesive forces cannot lift any weight of water, but cohesive forces can. Water in narrower tubes rises to a lower height than water in wider tubes. Water rises to a height where the adhesive forces go to zero.

Water rises to a height where the adhesive forces equal the weight of the water lifted

Most often we say that force causes acceleration. But when Evan took a ride in a rocket sled at Bonneville Salt Flats, blood was forced to the back of his brain, nearly blacking him out. Identify the cause of this force. Acceleration caused this force. Angular velocity caused this force. Gravitation caused this force. Velocity caused this force.

acceleration caused this force

An umbrella tends to move upwards on a windy day principally because air pressure is reduced over the curved top surface. buoyancy increases with increasing wind speed. trapped air under the umbrella, warms, and rises. all of the above

air pressure is reduced over the curved top surface.

a moving object has energy momentum velocity speed all of these

all of these

The name given to the shape of a sagging rope supported at its ends is a __________. Hints parabola hyperbola catenary semi-circle

catenary

a common pulley acts similar to a hydraulic press common lever tension producer gear

common lever

Is it tension or compression that strengthens an arch that supports a load? Both tension and compression Compression Neither tension nor compression - it's the cement. Tension

compression

When you do somersaults, you'll more easily rotate when your body is straight with both arms at your sides. straight with both arms above your head. no difference curled into a ball shape.

curled into a ball shape

Find the density of a 4.0-kg solid cylinder that is 15 cm tall with a radius of 4.2 cm .

density = 4800 kg/m3

efficiency E

efficiency = useful energy output / total energy input

What type of force holds atoms together in a crystal? Electromagnetic Gravitational Electric Magnetic

electric

Which has more skin: an elephant or a mouse? Which has more skin per unit of body weight: an elephant or a mouse? Elephant, mouse Mouse, elephant Elephant, both the same Elephant, elephant

elephant, mouse

Which of the following has the greatest outer surface area? Hints A grape An elephant A peach A tiger

en elephant

The buoyant force on a floating object is __________. Hints equal to the object's weight less than the object's weight more than the buoyant force than if submerged equal to the object's volume

equal to the objects weight

What is required to change the angular momentum of a system? Hints External force External torque Torque Force

external torque

while standing, your blood pressure is normally greatest in your feet same in each heart head

feet

the concept of pressure involves both force and volume area and volume force and area

force and area

the work that is one when twice the load is lifted the distance is ? -the same -twice as much -three times as much -four times as much

four times as much

which of these is not a form of solar energy wind energy hydroelectric power fossil fuel energy geothermal energy

geothermal energy

Which of the following has the greatest density? Lead Gold Uranium All the same

gold

Which has more mass, a liter of ice or a liter of water? a liter of water a liter of ice

liter of water

What is the cause of surface tension? An oil film The temperature of the water Molecular attraction Molecular repulsion

molecular attraction

When a tree branch is bent, the region in the center of the branch is the __________. tensile layer elastic layer neutral layer compressed layer

neutral layer

the most concentrated form of energy is geothermal fossil fuel nuclear wind

nuclear

What is the ultimate source of geothermal energy? Nuclear power in Earth's interior Gravity Kinetic energy of Earth in its orbit The Sun

nuclear power in Earth's interior

tangential speed E

radial distance x rotational speed v=r x w

when an ice cube in a glass of water melts, the water level falls remains the same rises

remains the same

Which of these is most elastic? Hints Steel Air Water Putty

steel

Why were so many vertical columns needed to support the roofs of stone buildings in ancient Egypt and Greece? Stone breaks under compression. Stone breaks along the neutral line. The columns are decorative elements. Stone breaks under tension.

stone breaks under tension

torque E

t=F x r

two cars are raised to the same elevation on service-station lifts. If one car is twice as massive as the other, compare their gains of potential energy -the car with twice the mass has half the gain of potential energy -the car with twice the mass has twice the gain of potential energy -both cars have the same gains of PE -the lass massive car has equal and opposite change of potential energy compared to the more massive car

the car with twice the mass has twice the gain of potential energy

mechanical energy

the energy due to the position of something and the movement if something

potential energy

the energy that is stored and held in readiness

When one does twice the work in twice the time, the power expended is _______. Hints three times as much twice as much. four times as much the same.

the same

A block of aluminum with a volume of 10 cm3 is placed in a beaker of water filled to the brim. Water overflows. The same is done in another beaker with a 10-cm3 block of lead. Does the lead displace more, less, or the same amount of water? more less the same amount

the same amount

Fossil fuels, hydroelectric power, and wind power ultimately get their energy from _______. potential energy greenhouse gases the Sun Earth's nuclear energy.

the sun

How does the weight of mercury in a barometer compare with the weight of an equal cross-section of air from sea level to the top of the atmosphere? They are equal. The answer depends on the cross-sectional area. The weight of the mercury is much greater. The weight of the air is much greater.

they are equal

Which is denser: an object that has a density of 1000 kg/m3 or one that has a density of 1 g/cm3? 1000 kg/m3 1 g/cm3 They are the same density. One is weight density and one is mass density, so it is impossible to compare them.

they are the same density

Suppose you're constructing a balcony that extends beyond the main frame of your house. In a concrete overhanging slab, should steel reinforcing rods be embedded in the top, middle, or bottom of the slab? bottom top middle

top

When you whirl a can at the end of a string in a circular path, what is the direction of the force you exert on the can? Radially outward from the center of the circle Toward the center of the circle Tangent to the circle in the direction of motion of the can Tangent to the circle and opposite in direction to the motion of the can

toward the center of the circle

Emily holds a banana of mass m over the edge of a bridge of height h. She drops the banana and it falls to the river below. Use conservation of energy to find the speed of the banana just before hitting the water.

v = √2gh

a hospital patient confined to a bed will be less likely to develop bed sores with a soft mattress firm mattress water bed none of these will help and the patient is doomed to hell

water bed

You wish to drill a hole through a horizontal I-beam supporting a bridge. To weaken the beam the least drill the hole through the web. lower flange. upper flange. all the same

web

gravitational potential energy E

weight x height PE = mgh

Why do we say that a blob of putty is inelastic? When deformed, it does not return to its original shape. It is made of rubber. It obeys Hooke's law. When deformed, it returns to its original shape.

when deformed, it does not return to its original shape

Why do we say that a spring is elastic? It is made of rubber. It does not obey Hooke's law. When deformed, it does not return to its original shape. When deformed, it returns to its original shape.

when deformed, it returns to its original shape

work E

work = force x distance w=fd

A certain spring stretches 5.6 cm when a load of 32 N is suspended from it. How much will the spring stretch if 42 N is suspended from it (and it doesn't reach its elastic limit)?

x = 7.4 cm

How much work is done on a satellite in a circular orbit about Earth? -The mass of the satellite times the circumference of the orbit -The gravity force on the satellite times the diameter of the orbit -The weight of the satellite times the circumference of the orbit -Zero

zero

Calculate the torque produced by a 42-N perpendicular force at the end of a 0.16-m-long wrench. T = lever arm x F

τ = 6.7 N m