The Problem:

The air inside an inflatable stand-up paddle board is 68.0°F and a gauge measures the pressure of this air to be 10.0 psi. If the volume of the air inside the board is reduced by 12.0% and the temperature increases to 102.2°F, what is the final gauge pressure of this air, in psi? (1.00 psi = 0.0680 atm)

Intermediate steps:

a.) This problem requires use of the ideal gas law, which can be expressed separately for the two relevant snapshots in time. What is the ideal gas law? [Consider: Which variables will not change between the two snapshots in time, that is between the initial and final states?]

b.) Only absolute values are used in the ideal gas law: absolute temperature, absolute volume, and absolute pressure. (“Absolute” means that a zero value is a true zero temp/pressure/volume.) Convert the initial and final temperature values (68.0°F and 102.2°F, respectively) along with the initial gauge pressure (10.0 psi) into absolute temperature and absolute pressure (in atm) values. Assume the air pressure outside of the paddleboard is 1.00 atm, or “standard pressure”. [Think: What is the reading on the pressure gauge when it is not being used to make a pressure measurement?]

c.) The volume of the board is not provided, only a relationship between the initial and final volumes. State this relationship in an equation (e.g. V_final = ___ V_initial). [Check: Which volume, final or initial, is greater? Does your equation/relationship correspond?]

d.) Without entering numerical values, write an expression for the final absolute pressure. [Recommended steps: (i) Using the ideal gas law, put all values that will change (the variables) on one side of the equal sign, and all values that are constant on the other. (ii) Equate the expressions for the variables from the initial and final states, as they equal the same constant expression. (iii) Solve for the final absolute pressure.] Now, numerically solve for final absolute pressure.

The solution:

e.) What is the final gauge pressure of the air inside the paddle board, in psi? [Please enter this answer as your final value. How many significant figures should be submitted?]

An attacker at the base of a castle wall 3.85 m high throws a rock straight up with speed 8.00 m/s from a height of 1.50 m above the ground. (a) Will the rock reach the top of the wall?

Yes No    

(b) If so, what is its speed at the top? If not, what initial speed must it have to reach the top?
m/s

(c) Find the change in speed of a rock thrown straight down from the top of the wall at an initial speed of 8.00 m/s and moving between the same two points.
m/s

(d) Does the change in speed of the downward-moving rock agree with the magnitude of the speed change of the rock moving upward between the same elevations?

Yes No    

(e) Explain physically why it does or does not agree.

A 3.9 g aluminum foil ball with a charge of +4.6×10−9 C is suspended on a string in a uniform horizontal E⃗ field. The string deviates to the right and makes an angle of 30∘ with the vertical. Determine the magnitude of the electric field.

1) When people sleep, their metabolic rate is about 2.6 * 10^-4 C/(s*kg). How many Calories does a 81 kg person metabolize while getting a good night's sleep of 8.5 hrs?

2) To determine the specific heat of an object, a student heats it to 100 °C in boiling water. She then places the 34.5-g object in a 151-g aluminum calorimeter containing 114 g of water. The aluminum and water are initially at a temperature of 20.0 °C, and are thermally insulated from their surroundings. If the final temperature is 23.6 °C, what is the specific heat of the object?

1). Physics ). . Place a positive and negative charge on the same y value, with different x-values.How does the field behave?. Does the field ever point only in the x or y

direction? Where does that occur in relation to the point charge?.

2). Open Charges and field simulation ( https://goo.gl/fHg5tj). Once the simulation opens, check the box next to Grid and next to values.

3). Place a single positive point charge in the simulation, and use an E-field sensor ( yellow balls) to measure the magnitute and direction of the electric field. How does the field change as you move away from the charge?

4).Now place a negative charge in the grid. How does the E-field change? What is similar and different to its behavior with the positive charge?

Question-1 Briefly sketch how Bohr derived the Rydberg’s empirical formula for atomic spectra using mix of classical mechanics and some ad hoc quantum assumptions. Indicate which steps in the derivation are motivated by classical mechanics and which are the quantum assumptions.

Question-2 Compute ionization energies of H, He+ and Li++ ions (Essentially all of them are one electron atoms) from ground state. Explain the trend.

Gina pushes a book across a table at constant speed. Fatima lowers a book from a high shelf down to her waist, where it comes to rest. Isidra holds a book at her waist while carrying it up stairs. Jin holds a book at her waist while carrying it across the room at constant speed. Who does zero work on their book?

A. Gina

B. Fatima

C. Isidra

D. Jin

A 3.9 kg mass is connected to a spring (k=179 N/m) and is sliding on a horizontal frictionless surface. The mass is given an initial displacement of +18 cm and released with an initial velocity of -16 cm/s. Determine the acceleration of the spring at t=1.9 seconds. (include units with answer)

To understand the concept of reactance (of an inductor) and its frequency dependence.

When an inductor is connected to a voltage source that varies sinusoidally, a sinusoidal current will flow through the inductor, its magnitude depending on the frequency. This is the essence of AC (alternating current) circuits used in radio, TV, and stereos. Circuit elements like inductors, capacitors, and resistors are linear devices, so the amplitude I0 of the current will be proportional to the amplitude V0 of the voltage. However, the current and voltage may not be in phase with each other. This new relationship between voltage and current is summarized by the reactance, the ratio of voltage and current amplitudes, V0, and I0: XL=V0/I0, where the subscript L indicates that this formula applies to an inductor.

What is the reactance XL of an inductor?

The speed of sound in seawater is approximately 1480 m/s. You are at a depth of 50.0m a. You ping the ocean bottom and receive the echo back 0.125 seconds later. How deep is the ocean at this point? b. If the frequency of the sound is 500.0 Hz, what is the wavelength of the sound? c. The ping coming back to the submarine has an intensity of as -80.0 dB. What is the intensity of the returning sound wave? d. Use the distance in part (b) and the answer in (c) to find the power of the reflected sound.

. Active sonar is used to determine the speed of an oncoming submarine. You send out a signal with a frequency of 500.0Hz. Your submarine is traveling at 13.0 m/s and the enemy is coming towards you at 9.00 m/s. Use the wave i.e. speed of sound as 1480m/s. a. What frequency will be reflected off the enemy? b. What frequency will be received by your submarine from the reflection? c. The enemy stops and sends his own signal of 600.0Hz. You receive his signal at what frequency? You are still moving towards him.

Assume air resistance is negligible unless otherwise stated.

Calculate the displacement in m and velocity in m/s at the following times for a rock thrown straight down with an initial velocity of 13.2 m/s from the Verrazano Narrows bridge in New York City. The roadway of this bridge is 70.0 m above the water. (Enter the magnitudes.)

(a)

0.500 s

displacement m

velocity m/s

(b)

1.00 s

displacement m

velocity m/s

(c)

1.50 s

displacement m

velocity m/s

(d)

2.00 s

displacement m

velocity m/s

(e)

2.50 s

displacement m

velocity m/s

Considering the illustrations for Concave and Convex mirrors.

Prove using geometry that the reflected rays reach the focal point f=R/2 in the limit as the incoming rays approach the principal axis.

Hint: Consider the triangle formed by the radius of curvature, principal axis, and reflected ray, and use the law of sines.

1.Check your car and find some electric/magnetic components, explain their working principle from physics. Such as battery, generator, alternator, starter, speed sensor, etc. Must list more than 4 components.