A simple insulator has a band gap of 4.0 eV, and the Fermi energy may be taken to reside in the middle of the gap. Estimate the probability of an electron at room temperature being in the conduction band.

Question B5

(a) A very hot 0.8 kg copper cylinder at temperature 365.84℃ is dropped into a 0.2 kg copper bowl contains 0.3 kg of water at 20℃. The final temperature of the system is 85℃. Given that specific heat of copper 386 J/kg·K and specific heat of water 4190 J/kg·K.

(i) Find the entropy change ∆S1 of the copper bowl and water.

(ii) Find the entropy change ∆S2 of the copper cylinder.

(iii) Find the net entropy change ∆Snet of the system. Is the process reversible or irreversible?

(b) What are the four processes of Carnot cycle?

A simple pendulum has a mass of 0.650 kg and a length of 7.00 m. It is displaced through an angle of 14.0° and then released. Using the analysis model of a particle in simple harmonic motion, calculate the following. (Give your answer to the thousandths place.)

(a) What is the maximum speed of the bob?


(b) What is the maximum angular acceleration of the bob? (rad/s²)

(c) What is the maximum restoring force of the bob?


(d) Solve parts (a)through (c) by using other analysis models. (Hint: you may need to use separate analysis models for each part.)

(e) Compare the answers.

A circuit consists of a large electromagnet that has an inductance of 52.0 H and a resistance of 8.00 ?, a dc 270 V power source, and an open switch - all connected in series.

A) How long after the switch is closed is the current equal to 10.5 A?

B) How long after the switch is closed is the current equal to 31.9 A?

Meteoroids, meteors, and meteorites are all related. Choose the correct time-ordered pairing.

What are the three types of meteorites?

What is the least common type of meteorite?

Which type of meteorite has the Widmanstatten pattern?

A car with mass 1309 kg is travelling north at a speed of 28.9 m/s. It collides at right angles with a truck (m=2733 kg) travelling east at 16.6 m/s and the two vehicles stick together after the collision. How much kinetic energy is lost during the collision?

• If a block of mass m at speed v collides inelastically with a block of mass M at rest, what is the final velocity of each block? What fraction of the initial energy is lost?

• Two identical circular hockey pucks of radius r traveling towards each other at the same speed v collide elastically. Their centers are separated by a vertical distance d, which is less than r. After the collision, with what angle relative to the initial path of the pucks will each one travel along?

• Explain the physics of Newton’s Cradle.

1. Derive Laws of Black Body Radiation from Wien’s Law: u_ν = ν³F(ν/T)
   1. What is Stephen’s Law?
   2. Please Prove Stephen’s Law from Wien’s Law
   3. Please Prove Wien’s Displacement Law from Wien’s Law

19 - 3 -4

A heat engine operates between a reservoir at 29°C and one at 341°C.

What is the maximum efficiency possible for this engine?

heat engine operates in a Carnot cycle between 88.0°C and 345°C. It absorbs 21,200 J of energy per cycle from the hot reservoir. The duration of each cycle is 3.00 s.

(a) What is the mechanical power output of this engine?
kW

(b) How much energy does it expel in each cycle by heat?

The sound from a busy highway contains a 500 Hz Fourier component whose power at the highway is 1.5 ✕ 10⁻⁶ watt/m. (Ignore sound interactions with the ground).

(a)What are the sound intensity (in W/m²), the sound intensity level (in dB) and the loudness (in phon) of that Fourier component at a distance of 25 m from the highway?

intensity=?  W/m²

intensity level =? dB

loudness=?  phon

(b)What are the sound intensity (in W/m²), the sound intensity level (in dB) and the loudness (in phon) of that Fourier component at a distance of 50 m from the highway?

intensity=? W/m²

intensity level=? dB

loudness=? phon

A package of mass 50 kg sits on an airless asteroid of mass 1.25 x 10^13 kg and radius 1000 m. We want to launch the package straight up so that it reaches a maximum distance of 4000 m from the center of the asteroid, where it will be picked up by a waiting ship before it can fall back down. We have a powerful spring whose stiffness is 1000 N/m. How much must we compress the spring to release it with the energy needed to reach the required altitude?

A 8.50 kg mass is attached to the end of a hanging spring and stretches it 28.0 cm. It is then pulled down an additional 12.0 cm and then let go. What is the maximum acceleration of the mass? At what position does this occur? What is the position and velocity of the mass 0.63 s after release?

A balance and torque experiment is conducted with an UN-balanced ruler.

Length of the ruler: 1 m

Mass of the ruler: 149 g

The pivot is at the 32-cm mark.

A 77-g mass is located at the 24-cm mark of the ruler.

We want to balance the ruler by placing another mass at the 11-cm mark.

What should be magnitude of this additional mass?

A balance and torque experiment is conducted with an UN-balanced ruler.

Length of the ruler: 1 m

Mass of the ruler: 97 g

The pivot is at the 61-cm mark.

A 45-g mass is located at the 33-cm mark of the ruler.

We want to balance the ruler by placing a 207-g mass somewhere on the ruler.

At which mark on the ruler should we place the 207-g mass?

you have preparing your coffee in the morning. it comes out of the brewrt at a whopping 100c and you pour about 3kg of coffee. you then add in 1kg of cream at 15c to customize your taste and 1 ice cube with mass of 0.05kg at 0c. if we can assume both the cream and coffee behave like water, what will be the final temperature of your coffee mixture?

(let coffee= 1, cream=2, ice cube=3)

Question: calculate the final equilibrium temperature.