A student has a flat board and a small block. From the experiment, he wants to determine the coefficients of static and kinetic frictions.

A) Placing the block on the board, the student raises one end of the board slowly. When the board has a vertical height of 20.0 cm, the block begins sliding down the length of the board, 77.3 cm. Using this information, what is the coefficient of static friction?

B) As the block slid down the length of the board, it accelerated. If it took 1.60s for the block to slide down the full length of the board, calculate the coefficient of kinetic friction.

C) The student now lowers the angle of the board from parts A and B and pushes the block to start it moving. At what angle will the block slide down at a constant speed?

D) The student now sets the board at and angle of 30.0 degrees. As they put the block on the board, they begin pushing on the block, perpendicular to the board, to prevent it from sliding. What is the minimum force needed to do this?

A river 108.4 m wide flows toward the south at 30.5 m/min. A girl on the west bank wishes to reach the east bank in the least possible time. She can swim 108.4 m in still water in 1.60 min.

(a) How long does it take her to cross the river?

(b) How far downstream does she travel?

c) What is her velocity relative to land? Magnitude and direction

(d) What is the total distance she travels?

(e) In what direction must she swim if she wishes to travel straight across the river?

A sheet of glass is coated with a 495-nm-thick layer of oil (n = 1.42).

1- For what visible wavelengths of light do the reflected waves interfere destructively?

2- What is the color of reflected light? ( Yellow,Green-blue,Red, or Orange )

3- What is the color of the most part of transmitted light? ( Orange, Yellowish green, Red,or Blue ).

Please, show me.

A 2.49-kg cart on a long, level, low-friction track is heading for a small electric fan at 0.25 m/s . The fan, which was initially off, is turned on. As the fan speeds up, the magnitude of the force it exerts on the cart is given by at2, where a = 0.0200 N/s2.

Part A

What is the speed of the cart 3.5 s after the fan is turned on?

Part B

After how many seconds is the cart's velocity zero?

b) How much work in Joules must be done for a heat transfer of 4.925x10^6 J from the cold environment?

c) What is the cost of doing this, if the work costs 16.5 cents per 3.60x10^6 J (a kilowatt-hour)?

d) How many Joules of heat transfer occurs into the warm environment?

Why are Sunspots dark and how/why do scientists think they are formed?

Sphere A of mass 0.600 kg is initially moving to the right at 4.00 m/s. sphere B, of mass 1.80 kg is initially to the right of sphere A and moving to the right at 2.00 m/s. After the two sphere collide, sphere is moving at 3.00 m/s in the same direction as before.

(c) Sphere B then has an off-center collision with sphere C,
which has mass 1.20 kg and is initially at rest. After this collision,
sphere B is moving at 19.0° to its initial direction at
What is the velocity (magnitude and direction) of sphere C after
this collision?

(d) What is the impulse (magnitude and direction)
imparted to sphere B by sphere C when they collide?

(e) Is this second collision elastic or inelastic?

(f) What is the velocity (magnitude and direction) of the center of mass of the system of three
spheres (A, B, and C) after the second collision? No external forces
act on any of the spheres in this problem.

1. Explain what is work (physics term)? What is kinetic energy? The relationship between the work

done by the net force on the object and kinetic energy of object.

2. How do you know the work-energy theorem is true? (hint: describe clearly how it works in yourexperiment or in real life)

So Gerard 't Hooft has a brand new paper (thanks to Mitchell Porter for making me aware of it) so this is somewhat of a expansion to the question I posed on this site a month or so ago regarding 't Hoofts work.

Now he has taken it quite a big step further: http://arxiv.org/abs/1207.3612

Does anyone here consider the ideas put forth in this paper plausible? And if not, could you explain exactly why not?

1) a) A charge of +5.00 nC is placed at the origin, and another charge of -3.00 nC is

placed 2.5 cm west of origin, what is the electric potential at 3 cm east from origin?

b) Repeat a) at distance 5 cm north of origin.

c) Find the work done to bring another charge of -5.00 nC from infinity to the point at 3 cm east from origin.

with the same three capacitors in parallel. How is this different than the result in series?

2) Three resistors of 25.00 ?, 17.00 ? and 13.00 ? are connected in series to a source with a potential difference of 3.00 V.

a) What is the equivalent resistance?

b) What is the the current in each resistor, and what is the potential difference across each resistor?

c) What is the power in each capacitor?

with the the same resistors in parallel. How is this different than the result in series?

A circus act involves launching a human being from a cannon resting on the floor. The human has a 50 kg mass and is launched at a speed of 12 m/s, in a direction 30° up from the horizontal. The cannon has a mass of 110 kg. (a) Considering the system as cannon + human, state why the x-component of the momentum is conserved. (b) Find the recoil speed of the cannon. (c) It would be dangerous to use explosives, so the performer is actually launched from a loaded spring inside the barrel, compressed 1.7 m from its equilibrium position. Find the spring constant needed to achieve the launch + recoil. (d) You will note that the y-component of the net momentum is NOT conserved, since the performer flies up in the air. Why is the x-component conserved but the y-component not?

A cylinder of radius 2.59 cm and a spherical shell of radius 6.72 cm are rolling without slipping along the same floor. The two objects have the same mass. If they are to have the same total kinetic energy, what should the ratio of the cylinder\'s angular speed to the spherical shell\'s angular speed be?

A 3.05-kg ball of clay is thrown downward from a height of 2.75 m with a speed of 5.01 m/s onto a spring with k = 1750 N/m. The clay compresses the spring a certain maximum amount before momentarily stopping. What is the total work done on the clay during the spring's compression? Also, how would one go about solving for that?

A hollow aluminum cylinder 23.5 cm deep has an internal capacity of 2.000 L at 17.0°C. It is completely filled with turpentine at 17.0°C. The turpentine and the aluminum cylinder are then slowly warmed together to 75.0°C. (The average linear expansion coefficient for aluminum is 24 ✕ 10−6°C−1, and the average volume expansion coefficient for turpentine is 9.0 ✕ 10−4°C−1.)

(a) How much turpentine overflows? cm3

(b) What is the volume of turpentine remaining in the cylinder at 75.0°C? (Give your answer to at least four significant figures.) L

(c) If the combination with this amount of turpentine is then cooled back to 17.0°C, how far below the cylinder's rim does the turpentine's surface recede?

1.Explain in a short paragraph what a heat engine is and what it does. Make sure your explanation includes: (a) what is the purpose of a heat engine, (b) what does a heat engine need to achieve that purpose, and (c) what limits how well a heat engine can achieve that purpose ("efficiency")?

2.The idea that evaporation is a cooling process is a familiar and intuitive one. What sounds counter-intuitive at first is this claim: "Boiling is a cooling process" (but hopefully the first two videos above have convinced you of the veracity of this claim). Explain how boiling is a cooling process. Make sure your explanation refers to latent heat (or "latent heat of vaporization", to be specific). What is the key difference between evaporation and boiling?