Touching hot objects is painful due to the high-velocity impacts of many, many atoms. Touching extremely cold objects can sometimes be painful as well. If the atoms/molecules in a cold object are moving very slowly, what causes the painful sensation?

An ideal gas undergoes the following Carnot Cycle. It starts in a chamber of volume .0065 m³ and temperature 345 Kelvin and pressure 630 kPa (state 1). It is allowed to expand isothermally to a volume of .01066 m³ (state 2) while heat is added to the gas.  Then it expands adiabatically to a volume of .01784 m³ (state 3). Then, it is compressed isothermally to a volume of V_f m³ (state 4) while heat is extracted from the gas.  Finally, it returns to its initial state in an adiabatic process.  (The gamma of the gas, γ = 1.28,  C_v = 3.5R).

How much heat is added in the 1^st isothermal process and the efficiency of this engine?

a.)1.878 kJ, 11.2%

b.) 2.029 kJ, 11.2%

c.) 2.029 kJ, 13.6%

d.) 2.334 kJ, 13.6%

e.) 2.334 kJ, 15.8%

Consider the retarded scalar and vector potentials. Show that they satisfy the Lorentz gauge.

A flaggpole of mass 5km and length 3.0 m is hinged at a wall and supported by a horizontal position by a cable affected to the flagpole at 2.0 M from the wait. The cable makes an angle of 25 with the horizontal. An iron plate of mass 1.5 kg is hanged at the free end of the flagpole.

A. what is the tension in the cable.

B. What is the horizontal force excerted on the hinge of the wall.

C. What is the vertical force excerted on the hinge at the wall. Use (+) or (-) to indicate direction

Monochromatic coherent light with a wavelength of 632.8nm is incident on a double slit system with a slit separation of 0.15mm. What is the separation between the third bright spot from the center and the seventh bright spot from the center?

(2a) A 4750.0 kg open train car is rolling on frictionless rails at 24.3 m/s when it starts pouring rain. A few minutes later, the car's speed is 18.0 m/s. What mass of water has collected in the car?

(2b) Two 485.0 g blocks of wood are 2.65 m apart on a frictionless table. A 23.1 g bullet is fired at 384.5 m/s toward the blocks. It passes all the way through the first block, then embeds itself in the second block. The speed of the first block immediately afterward is 1.07 m/s. What is the speed of the second block after the bullet stops?

(2c) A 2.67 kg sphere makes a perfectly inelastic collision with a second sphere that is initially at rest. The composite system moves with a speed equal to one third the original speed of the 2.67 kg sphere. What is the mass of the second sphere?

Explain what is interference, refraction and reflection in waves.

Intro to Astronomy:

Please CONCISELY answer these questions, thank you!

1.) Suppose the amount of mass in a black hole doubles, does the event horizon change? If so, does it grow, shrink, or stay the same size? And what physical force limits the growth of supermassive black holes?

2.) Assume that the distance from one edge of the Milky Way Galaxy to the other is 1 cm, with this same scale how far away is the Andromeda Galaxy? Why do astronomers believe that gravitation in the universe is dominated by dark matter?

3.)Consider a stellar black hole that used to be a 100 solar mass main sequence star and a planet orbiting around it at 10 AU. From the planet's position (pretend it survived the Type 2 supernova), was the star or black hole a stronger gravitational object?

Of the fundamental forces, the text claims that “gravity dominates on very large scales.” However, both the gravitational force and the electric force decrease in proportion to the inverse squared distance. Explain why the electric force isn't as strong as the gravitational force at very large distances.

. (a) Draw the basic setup for quantum key distribution.

(b) Explain the “intercept-resend” attack that Eve can attempt (draw a simple figure).

(c) Explain how this attack is thwarted by the quantum key distribution protocol. How can Eve’s attack be detected?

(d) What does the security of quantum key distribution rely on fundamentally?

(part 1 of 2)

An electric car is designed to run on a bank of batteries with a total potential difference of 29 V and a total energy storage of 2.2×107 J. If the electric motor draws 6.8 kW, what is the current delivered to the motor? Answer in units of A.

(part 2 of 2) If the electric motor draws 6.8 kW as the car moves at a steady speed of 47.0 m/s, how far will the car travel before it is “out of juice”? Answer in units of m.

You have set up an experiment where two Stern-Gerlach analyzers sequentially measure spin along the z-axis. The first analyzer allows particles with spin up along z to pass. The second analyzer allows particles with spin down along z to pass. Between the two analyzers is a magnetic field aligned along +x. Your experiment sends identical spin-1/2 particles at speed v along the y-axis through the analyzers, which are separated by a distance Δy. What is the smallest distance Δy that will transmit 50% of the particles passed through the first analyzer through the second analyzer?

Show that if qd≫1 the probability for tunneling through a potential barrier of width d is proportional to e^(-2qd). Plot this function and explain the implications.