I am wondering whether the five1 units of the natural unit system really is dictated by nature, or invented to satisfy the limited mind of man? Is the number of linearly independent units a property of the nature, or can we use any number we like? If it truly is a property of nature, what is the number? -five? can we prove that there not is more?

In the answers please do not consider cgs units, as extensions really is needed to cover all phenomenon. - or atomic units where units only disappear out of convenience. - or SI units where e.g. the mole for substance amount is just as crazy as say some invented unit to measure amount of money.

Sound source A is located at x = 0, y = 0, and sound source B is located at x = 0, y = 2.0 m. The two sources radiate coherently and in phase. An observer at x = 15.8 m, y = 0 notes that as he takes a few steps from y = 0 in either the +yor −y-direction, the sound intensity diminishes. What is the lowest frequency, and the next to the lowest frequency of the sources that can account for that observation? (Enter your answers from smallest to largest.)

kHz

kHz

a) What are the different types of “light” (electromagnetic waves), starting from radio waves? Why do you think we can only see such a small portion of the electromagnetic spectrum? Why don’t we see X-rays or microwaves?

b) Explain what a photon is and what property of photons relates to different colors of light.

c) What is the frequency of light that has a wavelength of 400 nm? What is the color of such light? What is the energy of a photon of such light (in eVunits)?

A 1.8-cm-tall object is 28cm  to the left of a lens with a focal length of 14cm . A second lens with a focal length of -6cm  is 39cm  to the right of the first lens.

Part A:

Calculate the distance between the image and the second lens.

Part B:

Calculate the image height.

Please show how you obtained the answers!

If everyone living on Earth moved to the equator, the length of day would change. Calculate the change in the day length. (professor gave the hint to use r=R_E*cosΘ)

I know it has to do with conservation of momentum (L_i=L_f) and that the day will lengthen by less than a second, but I'm not sure how to estimate the inertia of people living around the world like normal unless I use the moment of inertia for a thin shell (2/3mr²) and I don't know where the equation above is supposed to be used....or what theta he is talking about.

An object with total mass m_total = 6.3 kg is sitting at rest when it explodes into two pieces. The two pieces, after the explosion, have masses of m and 3m. During the explosion, the pieces are given a total energy of E = 44 J.

1)What is the speed of the smaller piece after the collision? (m/s)

2)What is the speed of the larger piece after the collision? (m/s)

3)If the explosion lasted for a time t = 0.028 s, what was the average force on the larger piece? (N)

4)What is the magnitude of the change in momentum of the smaller piece? (kg-m/s)

5)What is the magnitude of the velocity of the center of mass of the pieces after the collision? (m/s)

• Draw a diagram including your chosen coordinate system.

• Label all quantities in the diagram using standard notation.

• List the known and unknown quantities. Circle the unknowns.

• Identify the equation you are using and show all your work. • At the end of each problem, check your answer. Do the units match? Is the answer reasonable? Does the plus or minus sign make sense?

3. In the Daytona 500 auto race, a Ford Thunderbird and a Mercedes Benz are moving side by side down a straightaway at 71.5 m/s. The driver of the Thunderbird realizes that she must make a pit stop, and she smoothly slows to a stop over a distance of 250 m. She spends 5.00 s in the pit and then accelerates out, reaching her previous speed of 71.5 m/s after a distance of 350 m. At this point, how far has the Thunderbird fallen behind the Mercedes Benz, which has continued at a constant speed?

The numerical aperture of an instrument is 0.969. How far apart are the lines on a certain shell if they are just barely resolved when viewed with green light (548 nm)?

A 1.5 kg block of wood is launched up a wooden ramp that has a 40-degree incline. The initial speed of the block is 12 m/s. The coefficient of static friction is 0.4 and the coefficient of kinetic friction is 0.20. Ignore air resistance.
A) Draw the incline with the block at the bottom of the ramp and at the top of its slide. Label with a coordinate system. List all known quantities.
B) Draw free body diagrams for the block sliding up the incline and down the incline. Label all forces and acceleration.
C) What is the normal force on the block?
D) What is the acceleration as the block moves up the ramp?
E) How far up the ramp does the block travel?
F) What is the static frictional force on the block when it stops? Is it enough to hold the block there?

A nearsighted man uses his ideally prescribed eyeglasses that have a refractive power of −2.60 diopters. He would like a prescription for contact lenses. What is the correct contact lens prescription if he normally wears his eyeglasses a distance of 2.7 cm from his eyes?

Astronomy Mysteries Today

1.what’s dark matter? Why do astronomers believe it exists?

2. what’s dark matter? Why do astronomers believe it exists?

3. What’s a black hole? What’s the difference between stellar balck hoiles and galaxy black holes? Why is it black?

4. People ask “who” made the original mass that expanded in the Big Bang. What is one natural, as contrasted with supernatural, explanation for how the world began?

5. What may have been the first particles formed… before protons and neutrons, before atoms, before elements, before molecules?

The Hyundai Blue-Will Plug-In hybrid is a compact 4-door, 4-seat sedan.It is a test bed of new ideas, including panoramic glass roof with solar
cells for recharging batteries, a thermal generator that converts hot exhaust gases into electricity, drive-by-wire steering, lithium polymer
batteries, and touch screen controls. Blue-Will promises an EV driving range up to 40 miles on a charge and an economy rating up to 100 mpg.
Helping to achieve those numbers is a direct injection 1.6 liter 152-hp four, a CVT and a 100 kw electric motor..

1. A Hyundai Blue-Will hybrid is capable of an acceleration of 4.3 m/s. It has a mass of 770 kilograms of steel, 180 kilograms of iron, 110 kilograms of plastics, 80 kilograms of aluminum, 60 kilograms of rubber, 20 kilograms of glass, and 8 kilograms of other materials. The driver has a mass of 85 kg. a Sketch the system of the Blue Will b.Sketch the system of the driver c. What is the force on the driver from the acceleration? d.Compare the force of the car on the driver to the driver’s weight, using a ratio. 2. The Hyundai Blue Will hybrid is driving at a velocity of 125 kph, and crashes into another car traveling at a velocity of 35 kph. Assuming the drivers are of comparable mass, and the car bumpers lock on impact: a. What is the final velocity of the cars? b. If the famous Blue Will crashes into a tree, instead, in 2.6 seconds, what is the impulse? c. What is the total force exerted by the tree in stopping the Blue Will? 3. The Famous Blue Will hybrid is being driven at a velocity of 75 kph when the driver sees a tree ahead. a. The driver locks his brakes, causing the car to skid. The coefficient of friction of rubber on dry concrete is 1.0 (static) and 0.7 (kinetic). How much force will the brakes apply to the car? What difference would it make if the driver pumped the brakes? b. After 1.0 second of braking, what will be the car’s velocity? c. How far in advance will the driver need to start braking to avoid the tree? 4. The Hyundai has about the same drag as a Camry (about 0.36) and air has a density of about 1.21 kg/m3. The cross section of the Hyundai is about 1.5 m × 1.5 m. Take the torque provided by the engine at speed as about 250 lbf. a. What is the force applied by air resistance at 75 kph? b. Would this help the driver avoid hitting the tree in the previous problem? Why or why not? c. What is the maximum velocity of the car? Is this answer reasonable? Why or why not?

Holly Hiker goes for a walk which consists of three parts:

1: Walks 6.00km at an angle of 60.0 degrees west of north

2: sits for lunch for 30 minutes

3: Walks 4.00km at an angle of 75.0 degrees north of west for 45 mins ( or 0.75 hours)

a) draw a vector diagram showing Holly's walk. Include both legs and the resultant

b) Write the two walking legs of the trip in unit vector notation

c) Find Holly's displacement and average velocity( in both polar and unit vector notation)

Thanks so much in advance!!

a ceiling fan consists of a small cylindrical disk with 5 thin rods coming from the center the disk has mass md=2.6 kg and radius R=0.24 m the rods each has mass mr=1.4 kg and length L=0.75m1). what is the moment of inertia of each rod about the axis of rotation? 2). what is the moment of inertia of the disk about the axis of rotation? 3).what is the moment of inertia of the whole ceiling fan? 4).when the fan is turned on it takes t=3.6 s and a total of 12 revolutions to accelerate up to its full speed what is the magnitude of the angular acceleration? 5). what is the final angular speed of the fan? 6). what is the final rotational energy of the fan? 7).now the fan is turned to a lower setting where it ends with half of its rotational energy as before the time it takes to slow to this new speed is also t=3.6 s what is the final angular speed of the fan? 8). what is the magnitude of the angular acceleration while the fan slows down?