A stretchy cord has a diameter of 0.33 mm when lying loose off the spool. Loops are made on the two ends, 75.0 cm apart from knot to knot. The cord is hung vertically with one loop over a hook and the other with a 500 g mass hanging from it. After the mass is hung from it, the distance between the marks is now 79 cm.

a. What is the Young's modulus of the cord material?

b. If the same material also comes in a cord with diameter 0.66 mm, what would be its stretched length in the same scenario as above?

An electron and a proton are a distance r = 7 × 10^-9 m apart. How much energy is required to increase their separation by a factor of 3?

Well this is pretty noobish question and I am not sure how to ask.
When We talk we don't talk in an uniform frequency. Then how can one measure frequency of ones sound/voice ?
I am asking this cause several times I've heard people to say this is his/her frequency of voice. Is this a vague term ? or it has any real meaning ?

A high-speed flywheel in a motor is spinning at 500 rpm when a power failure suddenly occurs. The flywheel has mass 38.0 kg and diameter 80.0 cm. The power is off for 25.0 s, and during this time the flywheel slows due to friction in its axle bearings. During the time the power is off, the flywheel makes 160 complete revolutions.

A.) At what rate is the flywheel spinning when the power comes back on? (in rad/s)

B.) How long after the beginning of the power failure would it have taken the flywheel to stop if the power had not come back on? (in s)

C.) How many revolutions would the wheel have made during this time? (in rev)

The minimum stopping distance for a car from an initial 100 km/h is 60 m on level ground. What is the stopping distance when it moves (a) down a 10 degree incline; (b) up a 10 degree incline ? Assume that the initial speed and the surface are unchanged.

Asteroids X, Y, and Z have equal mass of 6.0 kg each. They orbit around a planet with M = 3.20×1024 kg. The orbits are in the plane of the paper and are drawn to scale. The three asteroids orbit in the same clockwise direction.

http://postimg.org/image/3yjgpptpp/

The angular momentum of Y is .... that of Z.

The angular momentum of Z at s is .... that at c.

The period of Y is .... that of Z.

The angular velocity of Z at c is .... that at i.

The angular velocity of Y at c is .... that at n.

The angular velocity of Z at c is .... that of Y at c.

The period of X is .... that of Y.

Options are Greater than, Less than, or Equal to

1. What are the main components of an eye’s anatomy?

2. What are all the similarities between the function of an eye and a camera? What are the differences?

3. How does the f-number of the eye change in different lighting conditions?

4. How do the lenses of the eye work (cornea, eye lens)? Which one has more power and why?

5. What is accommodation?

6. How does the eye accommodate with ciliary muscles?

7. How is color perceived on the retina with rods and cones?

8. Where are rods and cones, and where is your blind spot?

9. How does the eye adapt when light levels are lowered? What causes the Purkinje shift?

10. What is farsightedness (myopia) and nearsightedness (hyperopia)?

11. What exactly is happening in myopia and hyperopia to cause the blurred images on the retina (image forms in front of retina vs image forms behind retina)

From the window of a building, a ball is tossed from a height y0 above the ground with an initial velocity of 8.40 m/s and angle of 25.0° below the horizontal. It strikes the ground 6.00 s later.

(a) If the base of the building is taken to be the origin of the coordinates, with upward the positive y-direction, what are the initial coordinates of the ball? (Use the following as necessary: y0. Assume SI units. Do not substitute numerical values; use variables only.) xi = Correct: Your answer is correct. yi = Correct: Your answer is correct.

(b) With the positive x-direction chosen to be out the window, find the x- and y-components of the initial velocity. vi, x = 7.61 Correct: Your answer is correct. m/s vi, y = -3.55 Correct: Your answer is correct. m/s

(c) Find the equations for the x- and y-components of the position as functions of time. (Use the following as necessary: y0 and t. Assume SI units.) x = Correct: Your answer is correct. m y = Correct: Your answer is correct. m

(d) How far horizontally from the base of the building does the ball strike the ground? 45.68 Correct: Your answer is correct. m

(e) Find the height from which the ball was thrown. 197.88 Correct: Your answer is correct. m

(f) How long does it take the ball to reach a point 10.0 m below the level of launching? 1.4 Incorrect: Your answer is incorrect.

Can you help me with (f)?

A vertical scale on a spring balance reads from 0 to 235 N . The scale has a length of 10.5 cm from the 0 to 235 N reading. A fish hanging from the bottom of the spring oscillates vertically at a frequency of 2.65 Hz .

Ignoring the mass of the spring, what is the mass m of the fish?

Express your answer in kilograms.

On a hot day with a temp of 35 celsius, you blow across the open end of an empty test tube and produce the fundamental standing wave for the air column inside the test tube. The test tube acts like a 22 cm pipe open at one end and closed at the other.

What is the fundamental frequency?

What is the frequency of the next possible Harmonic?

A person standing nearby records a sound level of 50 dB. What is the sound intensity measured by that person?

Can anyone explain all the answer?

1. Horizontal force needed to keep a sled moving along dry (it means not wet) horizontal surface is 10 N. You increase this force up to 20 N. Neglect air resistance.  What can you say about character of motion of a sled now?

a. Sled will continue to move with the same speed.

b. Sled will accelerate for a while up to higher speed and then move with constant, higher speed.

c. Sled will accelerate indefinitely.

d. Sled will move with constant speed two times greater than initial.

2. You try to move a refrigerator of weight 2000 N applying force of 500 N. Refrigerator does not move. The force of friction acting of refrigerator is:

a. 2000 N

b. More than 500 N but less than 2000 N

c. Slightly less than 500 N

d. 500 N

e. Zero.

3. A person rides an elevator standing of a bathroom scale (people are doing strange things). Elevator moves up with constant velocity. What will be the reading of a bathroom scale?

a. more than mg

b. mg

c. less than mg

d. zero

4. Some force acts on an object sitting on the horizontal surface and it accelerates. We increase force twice and perform experiment again. If surface is frictionless, the acceleration of an object will increase:

a. Less than two times

b. Exactly twice

c. More than twice

d. Stays the same.

5. An object is sitting at rest on a horizontal table. Which one of Newton’s laws predicts that normal force acting on this object is equal in magnitude and opposite in direction to the force of gravity (weight) acting on this object?

a. First

b. Second

c. Third

d. Law of gravitation.

Now we will analyze the truck and load as two individual objects that interact with each other as they accelerateleft:2)We’ll start with analyzing the load.a.You discuss what forces are acting on the load with some fellow students. Everyone agrees that the Earth exerts a downward force on the load, but there is some disagreement about any other forces acting on the load. Use⃑as the force which the truck exerts on the load. The vertical component of ⃑is often given a specific name. If the load is simply resting in the bed of the truck (not tied down or in contact with the gate at the back of the bed), then the horizontal component of ⃑is also given a specific name. What are these names, and which way do the two components point (up or down; and left or right? Below, you can refer to the components of ⃑with the names you noted here if you would like to do so.

b. Draw a free body diagram for the load (using the same coordinate system that you used above).

c. Use Newton’s first two laws to determine the vertical and horizontal components of ⃑in terms of F drive, MT, mL, and g. (If one is zero, explicitly state that it is. Refer back to some of your conclusions from Question 1 about the acceleration of the load.)

Vertical Horizontal

Could you please demonstrate Brewster's angle and Critical angle in equation form and how to solve for it. still don't understand. Thank you

Part A) A solid sphere of mass M and radius R is mounted on an axle through its center. The axle is attached to a horizontal spring of constant k, and the sphere rolls back and forth without slipping. Derive an expression for the total energy of this system in terms of the displacement of the spring x, speed v of the center-of-mass of the sphere when its displacement is x, and M, and k.

Part B) Derive the expression for the angular velocity of the oscillation. Hint: Take the derivative of the energy with respect to time and set it equal to zero. The acceleration of simple harmonix motion is of the form alpha = -omega^(2) * x

(For part A I used 2/5MR^2 for the moment of inertia but it is saying it is wrong so please help)

Two capacitors,

C₁ = 16.0 μF

and

C₂ = 32.0 μF,

are connected in series, and a 15.0-V battery is connected across them.

(a) Find the equivalent capacitance, and the energy contained in this equivalent capacitor.

(b) Find the energy stored in each individual capacitor.

(c) If the same capacitors were connected in parallel, what potential difference would be required across them so that the combination stores the same energy as in part (a)?
V____

Which capacitor stores more energy in this situation, C₁ or C₂?

C₁C₂    Both C₁ and C₂ store the same amount of energy.