For each chapter (numbered), write a short essay on one of the given prompts (lettered). You
should have 11 essays total, one for each chapter. Each essay should be short (no longer than
one paragraph), but should thoroughly explain its point. For quantitative answers, you should
give both the answer and the work leading up to the answer. You may use your book and
internet sources, but none that respond (Ie wikipedia is allowed, yahoo answers is not). Please
do not directly quote sources. I will be on the virtual office hours if you want to ask me
questions.
1) Patterns of motion and equilibrium
a) Explain the basic differences between Aristotles theories of motion and Galileos.
Aristotle’s and Galileo’s theories of motion were both very brilliant but had many
different ideas, Aristotle’s idea of motion were that motion requires force, to make
an object move it needs force. He also believed that there were two types of
motion which were violent and natural. Galileo’s theory of motion was that all
objects are at rest.
b) Explain what is necessary for an object to be in equilibrium. For an object to be in
equlibruim it must experience no acceleration and its net force as well as the
torque acting on the object must be zero.
c) What is the difference between mass and weight? Mass is the amount of matter
within a body. Weight is the force delt on a body by gravity, for example if you go
to the moon your mass doesn’t change your weight will as gravity is weaker on
the moon hence the floating effect.
2) Newton's laws of motion
a) If the coefficient of friction between a cars tires and the ground is 0.7, what is the
maximum acceleration that car can experience?
b) What is necessary for an object to fall at a rate of ‘g’? for an object to fall at the
rate of G I believe the object must have weight and have some type of initial
acceleration like being thrown in the air or free falling. For example sky divers
accerlation depends on their mass as well as the height of initial jump and gravity
which is constant 9.81
c) A golf ball and a freight train collide. What do Newton's second and third laws say
about the collision? Newtons second law says that the net force of an object is
equivalent to the change of its velocity, and the third law says that as we know
every action has an equal and oppositve reaction. Akthough they weigh very
different they both exert the same force on one another , which goes back to the
example on the kid and the adult at the roller rink.
3) Momentum and energy
a) A 5kg object falls from a height of 20m. At the ground, padding allows it to come
to rest 0.2s after contacting the ground. What is the average force exerted by the
padding during those 0.2s?
b) Explain the similarities and differences between work-energy and impulsemomentum. Impulse momentum is the change in momentum, as momentum is
equal to mass times the change in velocity. Work energy is a little similar as all
work being done by all forces including gravity on a object is equal to the change
in kinetic energy which goes back to the newtons cradle idea.
c) Explain why simple machines don’t do any work of their own, and why they are
still useful? Simple machines don’t do any work on their own as they rely on a
past object to do something in order for it to work, for example my project on
newtonws cradle the last ball wouldn’t have moved without the first ball hitting it.
And they are useful as they don’t use much energy at rest and soley relies on the
past objects motion or force to get itself going.
4) Gravity, projectiles, and satellites
a) Why do you feel like your weight changes while riding a roller coaster, even
though the force of gravity does not? I believe this is true, because some of the
forces out rule each other for example the upward accelerations forces exceeds
the downward force causing your body to feel a temporary weightlessness
although the gravity doesn’t change. 7t6
b) Why does a satellite need to move fast to stay in orbit? The satellite needs to
move fast in order to defeat the gravitational pull its experiencing from earth, Its
fast speed also keeps the satellite in a straight line in the orbit.
c) In the absence of air resistance, why does an objects vertical motion change, but
its horizontal motion doesn’t? since the object is in flight ,with air resistance
absent the only force that would be laying on the object would be the weight of
the actual object, we know gravity is what causes weight and it pulls downward
vertically , so there would be no horizontal motion.
5) Fluid mechanics
a) A raft is made from wood that has a density of 750 kg/m³. What size does that
raft need to be to keep 200kg of cargo dry?
b) Why is the air pressure lower on the top of a mountain? The air pressure is lower
at the top of a mountain because amount of gas molecules in the air Is lower ,
that gas would be oxygen, that is why you would need some type of air supply at
such high altitudes. For example
6) Thermal energy and thermodynamics
a) When you put 0.3kg of water at 15°C on a stove, it takes 6 minutes for the water
to boil. What is the rate of heat added to that water? The rate of heat added to
the water is 297.50 J/s or Joules Per second, the picture of my work is uploaded
in the zip file.
b) Explain how an air conditioner can move heat from a cold room to a warmer
outside without violating the second law of thermodynamics. According to the
second law of thermodynamics, heat transfer happens from hot to cold and not
the other way around, however when the ac is doing this process it doesn’t
violate and cross the second law because the exchanging of the heat makes the
surroundings outside a little hotter than Inside, so it’s still obeying the law as hot
moving to cold or in this case a warmer outside.
c) Steel plates are commonly attached to each other by iron rivets. After a hot rivet
is inserted in a hole joining two plates, its blunt end is rounded with a
hammer, which is helped by the hotness of the rivet. How
does the hotness of the rivet also help make the fit tight
when it cools? When the rivet is Hot it expanded ever so
slightly to fit something that otherwise would not have fit
without it being heated. But when it cools it takes it retakes It
shape, making the rivet fit tightly around whatever was put
through it. For example, this is common when trying to put
roller bearings on a truck of a skateboard, the bearing may
be slightly small but when heated up it gets ever so slightly
bigger causing to fit tightly around the truck post.
7) Heat transfer and change of phase
a) Explain conduction, convection, and radiation. Conduction is
the transfer of thermal energy by direct contact such as
holding a hot object. Convection is the transfer of thermal
engery by the movement of a liquid or gas, for example the milk being prepared
in a coffe machine. Radiation is the transfer of thermal energy though thermal
given off, such as heating something cold up in the microwave.
b) Why does wetting your finger allow you to determine the direction that the wind is
blowing? The evaporation of the saliva or moisture on whichever side of your
finger becomes cold. That feeling allows you to determine direction of the wind
and where its coming from, but you have to be very still and calm for this to work.
c) I took a picture of my electric stove (right) shortly after removing a pot of boiling
water. Explain what is going on in that picture. That type of heating is an prime
example of conduction in which heat from the coil is transferred to the cookware.
The glow on the coils is due to a current being passed through it. You removed
the pot in which you probably turned the eye off so the current flow stopped
which is why you have a faint dark piece of coil in the center. However the coil is
still hot as it cools down.
8) Static and current electricity
a) You have two identical 30kg spheres. Both spheres have the same size, same
shape, and the same amount of charge. One of the spheres is sitting on the
ground (without being electrically grounded), the other is floating at a height of
2m.If the electric force is what keeps the second sphere floating, how much
charge on each sphere?
b) Explain charging by induction. Charging by induction is charging something
without actually touching and coming into contact with the other object. For
example, in the real world we have smartphones that can be charged without
plugging them in but plugging some base in that we sit the phone on. Both the
phone and the base have coils that create a magnetic field as one is negative
and one is positive, causing them to attract or repel depending on design.
Another example is a negatively charged balloon brought to two metal spheres
transferring and separating electrons although the sphere is neutral before
everything starts.
c) Why is it dangerous to plug a bunch of multi outlets into a single electrical outlet?
Its very dangerous to do that as all the current the appliances and things plugged
in at the same time creates an immense of amount of heat, as well as the
conductor starts to overheat as it cant conduct but so much.
9) Magnetism and electromagnetic induction
a) An electric motor has a phenomenon called back EMF, which limits the speed of
the motor. Where does this back EMF come from? The back emf is the
generative force output by an electric motor, the emf comes from the turning of
the coil inside the mag field. It opposes and acts against the intended voltage,
when the motor reaches its operating speed the back emf is increased which
drops the current and the item doesn’t uses as much power draw, for example
when the compressor kicks up on an refrigerator it draws a lot of current to get It
spinning until it has enough force to spin at normal operation.
b) One way to make a weak magnet is to align an iron nail so that
it is pointing north, then repeatedly hit it with a hammer. How
does this create a magnet? Hitting the nail hard repeatedly
forces the atoms and molecules to point themselves in one
direction which is usually the direction of the earth magnetic
pull which is similar to how the needle on compasses work.
10)Waves and sound
a) Why does the top of a harp have a wavy shape? The wavy
shape in the harp is there to primarily allow for more octaves for
the musician to play and drop down to. It also prevents the
string length from being linear instead of exponentially, hence
the reason why they can play such deep rich notes and tones.
b) Why is an echo weaker than the original sound? Echo’s Tend
to have shorter wavelengths which is why the volume of echo’s are usually lower
than the original. As well as the distance between the echo and the original. Its
volume and rich sound decrease as distance increases.
c) When astronomers look at the sun, they notice that the light emitted on one edge
of the sun is a slightly higher frequency than the light emitted at the other edge.
What does this tell us about the sun's motion? the sun does rotate however it is
very slow and I remember when you were telling’s us about light in the sky is blue
as light is being reflected off the ground and back up out out of the atmosphere,
but the sun has that red tint as the light is being separated as distance increases
and it’s a source of white light but without blue.
11)Light
a) You can get a sunburn on a cloudy day, but you won’t get a sunburn on a sunny
day if you are behind glass. Explain why. Due to clouds being clear and invisible
to ultra violet light waves it can provide little to no protection from the sun’s rays
which is why you can still get a sun burn, however glass is non transparent and
can cover you from some of the ultraviolet light causing sun burns.
b) Unpolarized light has an intensity of 60W/m². If it shines through two
perpendicular polarizers, the intensity is now 0W/m². If you put a third polarizer
between the two polarizers at a 45° angle to both, what is the intensity of light
now let through?
Bonus) Give me a physics based joke or meme.
“” we are not just fission For laughs “” LOL