Two identical blocks are placed 5 m apart. Each has a mass of 5 kg, is electrically neutral, and is made entirely of copper. Note: One copper atom has a mass of 1.055

I don't fully understand what would happen if we could travel at the speed of light. But I saw somewhere here that it would mean events happen out of order. But why is this a problem. It is said that cause has to happen before the effect, but why does this have to be linear?

And why is it that the speed of light is the maximum? I take it that light (photons?) are massless, so why can't they travel faster?

I am learning sailing on a 5m catamaran (Nacra 5). I am familiar with basic aerodynamics and the physics of the sail and keel.

We learned that when sailing closed hauled, too tight a mainsail tends to bring the boat up to the wind. And that the opposite is true for the jib. For example, one may steer up to the wind to come about, using the mainsail alone, by trimming it tight.

My question is why the trimmed mainsail in the above setup gives a larger torque.

This also seems opposed to the rule: "The more the mainsail is sheeted out the more the boat tends to come up.", as explained in http://www.sailtheory.com/mandf.html#sailsteering

Edit:

To my understanding, there are several possible competing effects involved:

(1) Effects that tend to INCREASE the mainsail torque to head up:

(1A) The direction of the sail force becomes more perpendicular to the boat. This increases the heeling torque. Since heeling motion happens faster than turning, the boat will heel more. This moves the sail force out, which increases the lever arm and the torque to head up. see diagram in: http://www.sailtheory.com/mandf.html#hellingstuur

(1B) The sail force moves backwards since the sail is stretched backwards. This increases the lever arm and the torque.

(2) Effects that tend to DECREASE the mainsail torque to head up:

(2A) The direction of the sail force becomes more perpendicular to the boat. Assuming that the force is perpendicular to the sail, and that the center of rotation is between the mast and the center of force, one sees that pulling the sail in, reduces the torque to head up, as can be seen in the following diagram:

diagram of the sail force torque

As Theta gets smaller, the torque Tau is reduced. This is opposed to what is stated in some of the answers below.

(2B) The sail force is reduced since the sail was pulled beyond its optimal angle of attack, thus losing lift and reducing torque.

(2C) Due to (2B) heeling torque is also decreased. With a similar reasoning to (1A) this decreases the lever arm and torque.

(2D) The sail force moves forward since the aft part of the sail is too flat and stalls. This shortens the lever arm and reduces torque. This is described in http://www.sailtheory.com/mandf.html#sailsteering

We know from reality that 1A+1B > 2A+2B+2C+2D. Considering heeling alone, we also know that 1A > 2C. It remains to be explained why in general this is the case.

Consider a rock that is thrown off a bridge of height 68 m at an angle ? = 22

A certain supernova remnant in our galaxy is an expanding spherical shell of glow-ing gas. The angular diameter of the remnant, as seen from Earth, is 22.0 arcsec. The parallax of the remnant is known to be 4.17 mas from space telescope measurements.Compute its distance in parsecs and radius in astronomical units.

A 2.50 mol sample of an ideal gas with a molar specific heat of CV = 5/2 R always starts at pressure 1.50 • 10^5 Pa and temperature 300 K. For each of the following processes, determine the final pressure (Pf, in kPa), the final volume (Vf, in L), the final temperature (Tf, in K), the change in internal energy of the gas (ΔEint, in J), the energy added to the gas by heat (Q, in J), and the work done on the gas (W, in J). (Due to the nature of this problem, do not use rounded intermediate values in your calculations—including answers submitted in WebAssign.)

(a) The gas is heated at constant pressure to 405 K.

P_f =_______ kPa

V_f =_______ L

T_f =_______ K

ΔE_int=_______ J

Q =_______ J

W =_______ J

(b) The gas is heated at constant volume to 405 K.

P_f =_______ kPa

V_f =_______ L

T_f =_______ K

ΔE_int=_______ J

Q =_______ J

W =_______ J

(c) The gas is compressed at constant temperature to 200 kPa.

P_f =_______ kPa

V_f =_______ L

T_f =_______ K

ΔE_int=_______ J

Q =_______ J

W =_______ J

(d) The gas is compressed adiabatically to 200 kPa.

P_f =_______ kPa

V_f =_______ L

T_f =_______ K

ΔE_int=_______ J

Q =_______ J

W =_______ J

A bumper car with mass m₁ = 117 kg is moving to the right with a velocity of v₁ = 4.1 m/s. A second bumper car with mass m₂ = 98 kg is moving to the left with a velocity of v₂ = -3.2 m/s. The two cars have an elastic collision. Assume the surface is frictionless. What is the velocity of the center of mass of the system What is the initial velocity of car 1 in the center-of-mass reference frame? What is the final velocity of car 1 in the center-of-mass reference frame? What is the final velocity of car 1 in the ground (original) reference frame? What is the final velocity of car 2 in the ground (original) reference frame? In a new (inelastic) collision, the same two bumper cars with the same initial velocities now latch together as they collide. What is the final speed of the two bumper cars after the collision?

Answer the following questions:Show all your work. Include formulae and units! EVERY TIME! Be sure to include meaningful,relavant diagram Don't try to squeeze everythingWrite down any formula used before plugging any numbers into it.

1.Eleven grams of Argon gas is used as the operating gas in a Carnot engine (an engine that uses the Carnot cycle to do work.The specifics of the cycle are:

a.The initial temperature of the gas is 300 K.

b.During the isothermal expansion, the volume of the gas increases from 0.0066 m³ to twice that volume.

c.During the adiabatic expansion, the gas temperature decreases to 200 K.

d.During the isothermal compression, the volume of the gas decreases from 0.0150 m³ to 0.0127 m³.

e.The adiabatic compression then takes the gas back to its initial state.

Note: The 2 temperatures given above are the operating temperatures of the Argon, NOT the temperatures of the reservoirs!

From this information determine:

I) The amount of energy that the engine absorbs from the hot reservoir during one complete cycle.

II) The amount of energy expelled to the cold reservoir for each cycle.

III) The net amount of work done by the engine per cycle.

IV) The engine

Is it energy?

Is it energy per unit volume?

Is it energy per unit time i.e power?

What is it?

I have just started looking into special relativity and I have come up with an intriguing gedanke, as Einstein himself called such theoretical thought experiments.

Imagine a space shuttle traveling through space at a constant velocity close to c. As the shuttle passes earth, a previously set-up camera starts broadcasting from earth to the shuttle. Since radio waves travel at the speed of light, the shuttle is receiving a constant transmission feed, assuming the camera is broadcasting 24/7.

Now, from what I have understood of special relativity so far, time will flow slower for the astronaut than for the earthlings. Hence, assuming v=0.8c, the astronaut will after 30 years have received a video transmission 50 years long!

Is my reasoning correct, that even though the transmission is live, the astronaut would actually be watching things that happened many years ago, while still receiving the "live" feed, which would be stored/buffered in the shuttles memory, thus making it possible for the astronaut to fast-forward the clip to see what happened more than 30 years after passing the earth?

My second question is, what happens when we consider the space shuttle to be at rest and the earth to be moving instead? If that would imply that it has been 50 years from the astronauts point of view, while only 30 years have passed on earth, then the astronaut would run out of video material after the first 30 years of watching the broadcast. Then what?

I hope it makes sense. Thank you!

At a flat gold course, a golfer hits a golf from the ground. The velocity of the bal immediely after being hit is 18.5 m/s at a derection of 38.0 degrees above the orizontal. The ball reaches the highest point of its projectile motion, and later, during the downward part of its motion the ball hits a branch of a tree. The branch is 3.00 m above the ground.

A) How much time elapses between the golfer hitting the ball and the ball hitting the branch?

B) How far does the ball travel horizontally before it hits the branch

C0 what is the velocity vector of the ball just before it hits the branch ?

There have been some very nice discussions recently centered around the question of whether gravity and the geometry and topology of the classical world we see about us, could be phenomena which emerge in the low-energy limits of a more fundamental microscopic theory.

Among these, @Tim Van Beek's reply to the question on "How the topology of space [time] arises from more fundamental notions" contains the following description of the Reeh-Schlieder theorem:

It describes "action at a distance" in a mathematically precise way. According to the Reeh-Schlieder theorem there are correlations in the vacuum state between measurements at an arbitrary distance. The point is: The proof of the Reeh-Schlieder theorem is independent of any axiom describing causality, showing that quantum entanglement effects do not violate Einstein causality, and don't depend on the precise notion of causality. Therefore a change in spacetime topology in order to explain quantum entanglement effects won't work.

which is also preceded with an appropriate note of caution, saying that the above paragraph:

... describes an aspect of axiomatic quantum field theory which may become obsolete in the future with the development of a more complete theory.

I had a bias against AQFT as being too abstract an obtuse branch of study to be of any practical use. However, in light of the possibility (recently discussed on physics.SE) that classical geometry arises due to the entanglement between the degrees of freedom of some quantum many-body system (see Swingle's paper on Entanglement Renormalization and Holography) the content of the Rees-Schilder theorem begins to seem quite profound and far-sighted.

The question therefore is: Does the Rees-Schlieder theorem provide support for the idea of building space-time from quantum entanglement? or am I jumping the gun in presuming their is some connection between what the theorem says and the work of Vidal, Evenbly, Swingle and others on "holographic entanglement"?

What is a virtual ground? I would like to know what it is

What variables affect the damping of a spring executing simple harmonic motion?

What are the independent variables, and what variables would need to be controlled in an experiment?

I'm attempting to complete an investigation where I measure the decrease in amplitude of a damped spring, and to prove the relationship between variables in the motion.

Thanks!

Select the answers which complete the statements below (e.g., if answer A completes the first statement, and answer B the others, enter ABBBB). A) positive B) negative C) neutral D) cannot tell

A positively charged glass rod repels an object suspended by a non-conducting thread. The charge on the object is ____ .

A positive point charge is brought near the outside surface of a neutral conducting sphere and released. The initial position of the point charge is on the positive x axis and the sphere is centred on the origin. The point charge moves in the ____ x direction. (If the point charge does not move, select answer C.)

A negatively charged glass rod attracts an object suspended by a non-conducting thread. The charge on the object is ____ .

A positively charged ball is brought close to a neutral isolated conductor. The conductor is then grounded, while the ball is kept close. If the ground connection is first removed and then the ball is taken away, the conductor has a ____ charge.

Two neutral metal spheres are mounted on insulating supports. They are connected by a wire. A positively charged glass rod is brought near sphere 1. The wire connecting the spheres is removed and the charged rod is then taken away. Now the charge on sphere 1 is ____ .