Hector read that the traditional drink in Tibet is tea with added butter. Inspired by this idea, he decides to investigate how a thin layer of fat on the top of a hot liquid affects the cooling of the liquid. He performs two different experiments.
Experiment 1: Hector pours 100 ml of boiling water into each of two Styrofoam cups and adds a thin (2.0-mm) layer of hot oil (at about 100∘C ) to one of the cups. He measures the initial temperature in the cups, waits for 10 minutes, and then measures the temperature again. His measurements are shown below.

Experiment 2: Hector puts two empty Styrofoam cups on separate precision scales and zeroes the scales. Then he pours 100 ml of boiling water into each cup and adds a 2.0-mm layer of hot oil to one of the cups. He records the initial readings of the scales, waits for 10 minutes, and then records the readings of the scales again. His data are shown below.

The surface area of the water in the cups is 3.0×10−3m2.

Part F

What other quantities relevant to the investigation can be determined or estimated from Hector's data?

a) The density of water

b) The number of moles of water

c) The rate of evaporation of oil

d) The density of oil

Two cars collide at an intersection. Car A, with a mass of 2000 kg , is going from west to east, while car B, of mass 1300 kg , is going from north to south at 17.0 m/s . As a result of this collision, the two cars become enmeshed and move as one afterwards. In your role as an expert witness, you inspect the scene and determine that, after the collision, the enmeshed cars moved at an angle of 65.0 ∘ south of east from the point of impact.

Part A: How fast were the enmeshed cars moving just after the collision?

v=_____________m/s

Part B: How fast was car AA going just before the collision?

Va=_____________m/s

A +7.50 μC point charge is sitting at the origin.

What is the radial distance between the 500 V equipotential surface and the 1000 V surface?

What is the distance between the 1000 V surface and the 1500 V surface?

Who discovered that thunderstorms give out electricity? Can you explain this process scientifically?

Which of the following statements are true for an atom with 3 energy levels? You can choose more than one answer.

When atomic electrons are excited to a higher level, they always return to their lowest energy level by jumping down one level at a time.

For a given battery voltage the kinetic energy of the free electron at the point of collision is higher if the atom is closer to the source of electrons.

When a free electron hits an atom, the atom is always excited to the highest energy level possible.

For a given position of the atom, the kinetic energy of a free electron at the point of collision increases as the voltage of the battery increases.

The number of different wavelengths emitted by the atom depends on the number of free electrons passing through the lamp.

The number of different wavelengths emitted by the atom depends on how much kinetic energy the free electron has when it hits the atom.

Photons are emitted as electrons in the atom jump up in energy.

In an inkjet printer, letters and images are created by squirting drops of ink horizontally at a sheet of paper from a rapidly moving nozzle. The pattern on the paper is controlled by an electrostatic valve that determines at each nozzle position whether ink is squirted onto the paper or not.

The ink drops have a mass \(\texttip{m}{m}\) = 1.00

A point charge 4.20 μC is held fixed at the origin. A second point charge 1.40 μC with mass of 2.80×10−4 kg is placed on the x axis, 0.260 m from the origin.

Part A: What is the electric potential energy U of the pair of charges? (Take U to be zero when the charges have infinite separation.)

Part B: The second point charge is released from rest. What is its speed when its distance from the origin is 0.600 mm?

Part C: What is its speed when its distance from the origin is 6.00 mm?

Part D: What is its speed when its distance from the origin is 60.0 mm?

Long, long ago, on a planet far, far away, a physics experiment was carried out. First, a 0.210-

kg ball with zero net charge was dropped from rest at a height of 1.00 m. The ball landed 0.450s later. Next, the ball was given a net charge of 7.80?C and dropped in the same way from the same height. This time the ball fell for 0.635s before landing.

What is the electric potential at a height of 1.00 m above the ground on this planet, given that the electric potential at ground level is zero? (Air resistance can be ignored.)

16g of nitrogen gas at STP are pressurized in an isochoric process to a pressure of 25atm .

A-What is the final temperature?

B-What is the work done on the gas? W=0 I got that , it's the correct answer

C-What is the heat input to the gas?

D-What is the pressure ratio pmax/ pmin ?

please answer this problem not simaler problems. thank u

Consider a pipe that is closed at one end. Sketch the standing wave pattern in each of the following situations; showing the regions of high and low air pressure variations (pressure antinodes and pressure nodes). Then formulate equations that relate the wavelength and frequency to the length of the pipe.

A. Tube with one end open ("closed tube"): fundamental

B. Tube with one end open ("closed tube"): first overture (3rd harmonic)

C. Find the ratio of the first overture and fundamental frequencies

D. Tube with both ends open ("open tube"): fundamental

E. Tube with both ends open ("open tube"): first overture (2nd harmonic)

F. Find the ratio between fundamental and first overture frequencies

A large crate is suspended by a light string. A bullet is fired horizontally into the crate and becomes firmly lodged inside it. After being struck by the bullet, the crate swings upward to a maximm height and then swings back up.

Just before the collision (time t1), the crate is at rest and the bullet moves horizontally with speed v0. Immediately after the bullet becomes lodged inside the crate (time t2) the bullet and crate move together with speed v. The crate reaches its maximum height at time t3.

1. Consider the time interval between times t1 and t2 (i.e., the collision between the bullet and crate).

A) During the collision, how does the force exerted on the crate by the bullet compare to the force exerted on the bullet by the crate? Discuss both magnitude and direction. Explain?

B) Is the total momentum of the bullet-and-crate system conserved during the collision? Explain how you can tell.

C) Is the total kinetic energy of the system conserved during the collision? Explain how you can tell.

2. Now consider the time interval from t2 to time t3 for the situation described (when the bullet and crate move together to a maximum height after the collision).

A) Draw a free body diagram for the bullet-crate system for an instant between times t2 and t3. Clearly label all forces.

Is the total momentum of the system conserved from tme t2 to time t3? Explain.

B) For each force you indicated on your free body diagram in part a, indicate whether the work done by that force on the bullet-crate system is positive, negative, or zero. Explain your reasoning.

Is the total mechanical energy (kinetic + potential) of the bullet-crat system conserved from time t2 to time t3? Explain.

3. Is it incorrect to say that the total mechanical energy of the bullet-crate system remains conserved for the entire motion. Explain why this is so, and indicate other types of energy into which the initial energy of the bullet could have been transformed.

A student is observing the oscillations of a mass on the end of a spring.   The spring has a force constant of 6 x 10^-5N/m, and the mass is 0.15 kg.   She pulls it 6 cm below equilibrium and lets it go.   She now writes an equation which she believes describes the motion of the mass. In her description, the y axis is vertical, and UP is positive.   Her equation is   
y = (3 cm) sin ( 0.02 sec^-1 t   + 3.14)

    (A) Does she have the amplitude right?   If not, what was right? If yes, explain.
    (B) Does she have the frequency right?   If not, what was right? If yes, explain.
    (C) Does she have the phase angle right? If not, what was right? If yes, explain.