Suppose that at least 19.6 eV is needed to free an electron from a particular element, i.e., to ionize the atom. What is the lowest frequency photon which can accomplish this? And, what is the corresponding wavelength for that photon? Give frequency for answer 1 and wavelength for answer 2.

Bob, who has a mass of 80kg , can throw a 480g rock with a speed of 26 m/s . The distance through which his hand moves as he accelerates the rock forward from rest until he releases it is 1.0m .

Part A : What constant force must Bob exert on the rock to throw it with this speed?

Part B : If Bob is standing on frictionless ice, what is his recoil speed after releasing the rock?

A water hose 2.85 cm in diameter is used by a gardener to fill a 28.0-liter bucket. (One liter = 1,000 cm³.) The gardener notices that it takes 1.00 min to fill the bucket. A nozzle with an opening of cross-sectional area 0.500 cm² is then attached to the hose. The nozzle is held so that water is projected horizontally from a point 1.00 m above the ground. Over what horizontal distance can the water be projected?
4.33 m *CORRECT*

EXERCISE HINTS:  GETTING STARTED | I'M STUCK!

Use the values from PRACTICE IT to help you work this exercise. The nozzle is replaced with a Y-shaped fitting that splits the flow in half. Garden hoses are connected to each end of the Y, with each hose having a 0.420 cm² nozzle.

(a) How fast does the water come out of one of the nozzles?

4.67 m/s *INCORRECT*
Some of the information you need is in the example. m/s

(b) How far would one of the nozzles squirt water if both were operated simultaneously and held horizontally 1.00 m off the ground? (Hint: Find the volume flow rate through each 0.420-cm² nozzle, then follow the same steps as before.)

2.11 m *INCORRECT*

Your expression is correct, but since your answer to part (a) is wrong, this answer is wrong too.

PLEASE HELP NO ONE SEEMS TO BE ABLE TO ANSWER THIS QUESTION CORRECTLY

In 200 words, how does a generator produce an electric current using electromagnetic induction? Give examples. Please explain in detail.

A roller coaster car with its passengers has a mass of 220 kg and it goes through a series of horizontal and vertical curves.

A. Draw the free body diagrams for the car going around a horizontal curve, the bottom of a vertical loop, and the top of a vertical loop in which the cart is upside down. Indicate the direction of the acceleration on each diagram.

B. If the car is moving at 25 m/s what is the smallest horizontal curve it can go around and not exceed a 4.5g limit on acceleration (g = 9.8 m/s2?

C. What speed does the car need at the top of a loop with a radius of 4.5 m in order for the car to experience weightlessness?

D. What is the apparent weight of the car at the bottom of a 4.5 m radius loop at 25 m/s?

Possible Duplicate:
Why does every thing spin?

So why would the Earth, or any planet for that matter, rotate along an axis? I know of no force which could come into play here, so i assume it just started off with an initial rotation. But where did this rotational energy come from? And are there any known planets which do not rotate?

Assuming no force accounts for earth's rotation, would it be true that the angular velocity of the earth would decrease(by a very very small amount), when bombarded by meteors(Due to an increase in the moment of inertia by the increase in mass of the earth i.e. the additional mass of the meteors)?

Physics Post Lab: Simple Machines

1) Which class of lever does the following belong to?

a. Pliers

      b. Bottle opener

      c. Scissors

      d. Fishing Rod

      e. Wheel Barrow

      f. Nail clipper

    g. Stapler

2) Does the single pulley magnify force, multiply speed, or simply change the direction of the applied force?

3) Archimedes said, “Give me a place to stand, and I will move the world”. Discuss what you think he meant by that!

4) Name three examples not already mentioned of wheel and axle systems.

An ac signal at a certain frequency is applied across a 40-mH inductor and a 100-Ω resistor. If the power factor of this circuit is 0.40, what is the value of the frequency?

A.160 Hz B.600 Hz C.910 Hz D.410 Hz C.200 Hz

An infinite straight wire has a linear charge density of 10 nC/m. What is the electric

field 0.50 meters away?

An ideal monoatomic gas is separated into two volumes V1 and V2 by means of
of a diathermic piston, such that each volume contains N atoms and both parts are
they find at the same temperature T0. The complete system is isolated from the
exterior by means of insulating walls.
The piston is externally manipulated reversibly until the two gases are
they find in thermodynamic equilibrium one with the other.
The purpose is to find the final temperature and the work done, or by the system, or
in the surroundings.
To answer this problem, follow the steps described below and answer
the questions that are asked:
a) What is the name of the type of process described? Show that
ΔS1 = -ΔS2
where ΔS1 and ΔS2 are the changes in the entropies of the two gases.
b) Write the equilibrium conditions in the final state and find the final volumes
On each side.
c) Find the final temperature. (Hint: Use the First Law on each side and the
result of subsection a)).
d) Find the total work due to the manipulation of the piston. Does the system do work
Or does the external agent do work on the system? Explain

w2.18.36

A 5.00 pFparallel-plate air-filled capacitor with circular plates is to be used in a circuit in which it will be subjected to potentials of up to 75.0 V. The electric field between the plates is to be no greater than 9850 N/C.

Part A: As a budding electrical engineer for Live-Wire Electronics, your tasks are to design the capacitor by finding what its physical dimensions must be.

Part B: As a budding electrical engineer for Live-Wire Electronics, your tasks are to design the capacitor by finding what its separation must be.

Part C: As a budding electrical engineer for Live-Wire Electronics, your tasks are to find the maximum charge these plates can hold.

start with water at an extremely cold temperature of -50ºC. Explain what happens as you slowly add heat to the water until it is at 175ºC. Explain both the macroscopic (or large scale) changes, as well as the microscopic (or atomic-level), changes.

An MRI technician moves his hand from a region of very low magnetic field strength into an MRI scanner's 1.60 T field with his fingers pointing in the direction of the field. His wedding ring has a diameter of 2.15 cm, and it takes 0.380 s to move it into the field.

(a) What average current is induced in the ring if its resistance is 0.0100 Ω? (Enter the magnitude in amperes.)

_________A

(b) What average power is dissipated (in W)?

_________W

(c) What average magnetic field is induced at the center of the ring? (Enter the magnitude in teslas.)

__________T

(d) What is the direction of this induced magnetic field relative to the MRI's field?

A. parallel

B. antiparallel

C. The magnitude is zero.

Select the correct answer

1- The current i through an inductor cannot change abruptly. The rate of change di/dt also cannot change abruptly. Both quantities must always be continuous. (True/ FALSE)

2- When a steady current flows through an inductor, there is no energy flow in or out of the inductor. (True/ FALSE ).

3- Long after an emf has been connected to an RL circuit and the current has stabilized, the voltage across the inductor is (Zero / None Zero)

4- When the current through an inductor increases, energy is (stored within / released from) the inductor. When the current decreases, energy is (stored within/ released from) the inductor.

5-The ballast used for a fluorescence tube keeps the current from growing unacceptably large (True/ False).

6-If you increase the inductance in an RL circuit, it takes __________ for the current to reach its final value. (More time/ Less time).

7-The voltage across an inductor is proportional to what? (The current through it /  The derivative in time of the current through it / The integral in time of the current through it).

8-If you increase the resistance in an RL, it takes ______________ for the current to reach its final value. (more time/ less time).

9- Immediately after an emf is connected to an RL circuit, the current through the inductor is ___________.(zero/ nonzero)

10- The final (steady state) current through a circuit containing a source of emf, a resistor, and an inductor does not depend of the value of the inductance. (True / false)

11- If the current doubles in an ideal solenoid, what happens to its magnetic energy density? (It is halved /  It is doubled/ It is quadrupled /It is quartered).

x   y
11   7.74
9   6.61
12   12.98
10   7.14
12   7.88
13   8.68
5   6.06
4   5.24
13   8.3
7   6.61
6   5.93...

Find the equation of the regression line.

y = mx + b