Physics Midterm 2.1

What is the force of a 500N woman standing on Earth? Why?

500N; Newtons measure force, and weight is the measure of gravitational FORCE acting on someone.

What do Newtons measure?

Force

What is weight?

The measure of gravitational force acting on someone.

Two objects move toward each other because of gravity. As the objects get closer and closer, theforce between them

Increases

According to Newton, when the distance between two interacting objects triples, the gravitationalforce is

1/9 as strong

What is the law of universal gravitation?

Every object in the universe attracts other objects with a force that is directly proportional to the product of their masses, and inversely proportional to the square of the distance between their centers

With each revolution of the Earth around its polar axis, we experience

two low and two high ocean tides. If the Moon were covered in water,

would there similarly be two tides per revolution? Why?

Tidal bulges yes, tides no; the Moon rotates exactly once every time it circles Earth, so the same side is always facing us. Even if two points on the planet bulged, there'd be no change of water height.

Passengers in a high-flying jumbo jet feel their normal weight in flight, while passengers in theorbiting space shuttle do not. This is because passengers in the space shuttle are... Why?

Without supporting forces; apparent weight, the type you can feel, requires a support force

Actual weight vs. apparent weight

The force of gravity on you vs. the force a body exerts on a supporting surface

The main reason ocean tides exist is that the pull of the moon

is greater on oceans closer to the moon and less on oceans farther from the moon

A black hole is

simply the remains of a giant star that has undergone a gravitational collapse

What is Kepler's first law of planetary motion?

The orbit of each planet around the Sun is an ellipse with the Sun at one focus

What are the two distances from the Sun in an elliptical orbit?

Perihelion (closest), aphelion (farthest)

A projectile is fired horizontally in a region of no air resistance. The projectile maintains itshorizontal component of velocity because

it is not acted on by any horizontal force

Newton's first law

An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force.

A projectile is launched from ground level at 35° above the horizontal and lands downrange. Whatother projection angle for the same speed would produce the same down-range distance? Why?

55°. Both of these angles add up to 90°. One stays in the air longer, but travels slower, and vice versa.

Atoms heavier than helium were made by

thermonuclear fusion

There are only about ___ kinds of atoms to form all substances.

100

What is the smallest particle known to exist?

Quarks (NOT atoms)

What atom has the most mass? Why?

Uranium; it has the most electrical charge in its nucleus and a large number of neutrons

What are atoms made up of? What is the lightest of these materials?

Protons, neutrons, electrons. Electrons are the lightest

What makes an element distinct?

Its number of protons

Why don't solids fall through one another, if most solid matter is empty space?

Electrical forces

If 1.0 gram of antimatter meets with 4.0 grams of matter, the energy released would correspond tothe energy equivalent of...? Why?

2g; 1g of antimatter also has positive mass, thus when it 1g of matter is annihilated with it, 2g total are converted to energy

What is an atomic number?

Tells you how many protons are in an atom's nucleus

What is an atomic mass number?

Tells you the number of protons and neutrons in a nucleus

If the mass of an object were tripled while its volume remained the same, its density would...? Why?

triple, density refers to how much mass is packed into a certain amount of space

When weight is applied to the top of a stone arch, do all of the stone blocksin the arch undergo compression or tension? Why?

Compression is when objects are pushed toward each other, while tension is pulling away. Arched bridges are designed to redirect weight to its supports on either side through compression of the stones.

96% of the human body is made up of the following elements:

hydrogen, oxygen, nitrogen, carbon

Which geometrical shape has the least surface area for a given volume?

Sphere

Two identical boxes are brim filled with spherical steel ball bearings - one

with uniform big-diameter bearings and the other with half-sized ones. If

you pour water and fill each box, which will take more water? Why?

Both the same; water fills any volume that is not occupied by something else. Double the amount of ball bearings may have more surface area, but they have the same volume.

A dam is thicker at the bottom than at the top partly because

water pressure is greater with increasing depth

A completely submerged object always displaces its own

VOLUME of fluid

When an object is partly or wholly immersed in a liquid, it is buoyed up

by a force equal to the liquid it displaced

A plasma differs from a gas in that

it is electrically conducting

tmospheric pressure is caused by the

weight of the atmosphere

Does the air in a room have weight, mass, or energy?

All three

When water is turned on in a shower, the shower curtain moves towards the water. This has to do with...

the pressure of a moving fluid; moving water sets the air (gas) around it in motion, meaning the pressure of the air inside the shower decreases

An egg rests at the bottom of a bowl filled with water. When salt is slowly added to the water the egg rises and floats, from which we conclude...

salt water is denser than fresh water, and denser than the egg

What is Bernoulli's principle?

as the speed of a moving fluid (liquid or gas) increases, its internal pressure decreases

A scale from which a rock is suspended reads 5 N when the rock is out of water and 3 N when the rock is submerged. Buoyant force on the rock is...

2N (5N-3N)

An astronaut on Earth notices that an ice cube in her soft drink floats with 9/10 of its volume

submerged. If she were instead in a lunar module parked on the Moon, the ice in the same soft drink would float with...? And why?

9/10 submerged; the flotation of an object is reliant on its density, not its weight, compared to the density of the fluid it is in

A swimmer cannot use a long hose to snorkel more than a meter deep because air

at the surface will not enter the higher-pressure region in the compressed lungs

What is specific heat capacity?

The amount of heat energy required to raise the temperature of a substane

What element warms up the fastest and why: iron, water, glass.

Iron, because it has the lowest specific heat.

The moderate temperatures of islands throughout the world has much to do with water's...

high specific heat

Ice has a lower density than water because

ice is made of open-structured, hexagonal crystals

Before ice can form on a lake, all the water in the lake must be cooled to

4 degrees celcius; water reaches its greatest density at this degrees, meaning warmer water isn't going to sink lower, and the top water will begin to cool to 0 degrees

When a bimetallic bar made of copper and iron strips is heated, the bar bends toward the iron strip. The reason for this is

Copper expands more than iron

During a very cold winter, water pipes sometimes burst. The reason for this is

water expands when freezing

Metals are both good heat conductors and good electrical conductors because of the

looseness of outer electrons in metal atoms

Energy transfer by convection is primarily restricted to

fluids

What is convection?

The transfer of a heat through the physical movement of a fluid

he planet Earth loses heat mainly by

radiation

What is inside the open pockets made by ice, which is less dense than water?

Nothing

The reason a life jacket helps you float is

the density of both you and your life jacket is less than the density of you alone

We do not observe tides in the community swimming pool because

all parts of it are practically the same distance from the moon

Someone throws a ball in the air. Assuming there is no air resistance, what component of velocity changes over time?

the vertical component

If the mass of the earth increased with no change in radius, your weight would...

Increase, because an increase in mass increases gravitational pull

If the radius of the earth increased with no change in mass, your weight would...

Decrease, because you become farther from the earth's center but the gravitational pull based on mass is the same

When do you experience weightlessness?

When there is no supporting surface (in a freely falling elevator, momentarily when you jump up from a chair)

The moon does not crash into the Earth because

the moon has sufficient tangential speed

Brownian motion is caused by

particles larger than atoms bumping into them

What is Brownian motion?

the random, jittery movement microscopic particles suspended in fluids (liquid or gas)

At which point in a planets orbit around the sun does it have the greatest potential energy?

At its furthest point from the sun, it has the most potential to fall quicker and quicker toward its closest point toward the sun

Molecules are the smallest subdivision of matter that...

still retains the chemical properties of a substance

Am I gonna be ok

yeah