Physics - September 2007

Can somebody please explain to me, why r.m.s voltage and not the average voltage is equivalent to d.c. Can you try and explain it physically, without resorting to P=IV, I know this side of it. I just can't seem to shake the picture in my head of a line denoting the average value as being the equivalent line of a d.c voltage. Why does it need that little bit extra to be equivalent? I hope this is clear.

2007-09-28 05:53:50 · 5 answers · asked by eazylee369 4

Physicist David Bohm former protege of Albert Einstein started the idea of a holographic universe since then many scientists and critics are becoming supporters but how do you go about proving that everything we assume is real is just a holographic enfoldment from within? Michael Talbot wrote a very detailed book about this called the holographic universe

2007-09-28 05:51:34 · 8 answers · asked by the11diamondsguy 1

2007-09-28 05:23:23 · 9 answers · asked by Anonymous

Is the microwave (radio wave) cancerous? If so, what distance from the equipment is safe?

2007-09-28 05:08:43 · 4 answers · asked by Theme 1

If you have a steel container with 2" thick walls, you fill it with water and weld a 2" plate on top you will have a strong container completely full of water.

If you then freeze this container how much pressure would be generated inside? Will the water still turn to ice? I know engines have cracked due to a lack of anti-freeze in winter and mountains are cracked via freeze-thaw.

Any ideas appreciated.

2007-09-28 05:04:20 · 4 answers · asked by Anonymous

if there r u balls of different masses in vaccum which one will fall down first ?

2007-09-28 04:44:10 · 5 answers · asked by pradeep m 1

You are conducting an experiment inside an elevator that can move in a vertical shaft. A load is hung vertically from the ceiling on a string. The tension in the string is measured to be exactly equal to the weight of the load. No other forces are acting on the load. Which of the following statements about the elevator are correct?

A.The elevator is an inertial frame of reference.
B.The elevator is not an inertial frame of reference.
C.The elevator may be at rest.
D.The elevator may be moving at a constant velocity upward.
E.The elevator may be moving at a constant velocity downward.
F.The elevator may be accelerating.
G.The elevator must be accelerating.

pls not only answer, i need to understand the concept.
Clear Explanations,

thanx

2007-09-28 03:53:20 · 3 answers · asked by Tommy 2

A vechicle on a straight downhill road accelerated uniformly from a speed of 4.0 ms-1 to a speed of 29ms-1 over a distance of 850 m, when the driver braked and stopped the vechicle in 28s.

a) Calculate the time taken to reach 29 ms-1 from 4 ms-1.

ii) Calculate its acceleration during this time.

b) Calculate the distance it travelled during deceleration.

ii) Its average deceleration as it slowed.

AS Physics past paper questions, I need help, thanks.

2007-09-28 03:08:23 · 2 answers · asked by Anonymous

If 230 volts is the r.m.s value, then 325.27 volts is the peak value and 207.07 volts is the average value for half the sine wave. So if 207.07 volts is the average value, how come 230 volts is the value that is equivalent to a d.c. voltage. I understand the maths when using the r.m.s voltage with r.m.s current to find the power, but I can't understand why the r.m.s voltage (or current) alone is equivalent to d.c and not the average of half a sine wave.

2007-09-28 02:15:48 · 5 answers · asked by eazylee369 4

I'm an electrician and when at work we always use I=P/V to find the current in a curcuit. However we use V=230 volts. Since 230 is an r.m.s value would the value of I obtained also be an r.m.s value, if so shouldn't we then find the average value of current for a more accurate reading.

2007-09-28 01:25:53 · 9 answers · asked by eazylee369 4

A m=2g ball is suspended by a 1 = 20 cm long string, in a constant electric field of E=1000 N/C. If the string makes an angle of 0 = 15 degrees with respect to the vertical, what is the net charge on the ball?

Please show work

2007-09-28 00:39:17 · 1 answers · asked by master 1

Why do you think that?
Could time travel be much easier than you think?

2007-09-27 20:50:53 · 11 answers · asked by Anonymous

absolute zero is 0 K(Kelvin), what could be the highest possible temperature?

2007-09-27 19:49:11 · 8 answers · asked by vj822 1

2007-09-27 19:42:46 · 3 answers · asked by JAMES 4

A bullet (mass m) hits a stationary block of wood (mass mb) and becomes embeddedin it. The co-efficient of kinetic friction between the block and the floor is uk. As a result of the impact the block slides a distance of D before stopping. What was the velocity v of the bullet?

2007-09-27 19:14:12 · 2 answers · asked by Anonymous

what is your average velocity ifyou drive a distance of 174 km at a speed of 50 kn/h, then the same distance at a speed of 66 km/h? answer in unites of km/h

2007-09-27 17:54:03 · 4 answers · asked by adidasblack16 1

A box weighing 70 N rests on a table. A rope tied to the box runs vertically upward over a pulley and a weight is hung from the other end (Fig. 4-37).

Determine the force that the table exerts on the box if the weight hanging on the other side of the pulley weighs:

(a) 27 N

(b) 65 N

(c) 104 N

2007-09-27 17:15:15 · 3 answers · asked by spksccrchica216 1

is it closer to ultraviolet or infrared?

2007-09-27 17:12:39 · 9 answers · asked by Scarlet 1

No obstructions, flatland. At approximately what distance would a vehicle be a dot? At approximately what distance would one be able to distinguish it as a vehicle?

2007-09-27 16:43:05 · 1 answers · asked by sebastian 2

2007-09-27 16:39:29 · 4 answers · asked by Scarlet 1

If a washing machine's drum has a radius of 25 cm and spins at 3.9 rev/s, what is the strength of the artificial gravity to which the clothes are subjected? Express your answer as a multiple of g.

2007-09-27 16:33:46 · 2 answers · asked by Anonymous

A 4.8 kg object is suspended by a string from the ceiling of an elevator.

Acceleration of gravity= 9.8 m/s^2

a) Determine the tension in the string if it is accelerating upward at a rate of 0.8 m/s^2.

b) Determine the tension in the string if it is accelerating downward at a rate of 0.8 m/s^2.

Answer in units of N.

2007-09-27 16:16:16 · 2 answers · asked by Anonymous

If you were on a 26.9 degree slope and an avalanche started 450 m up the slope, how much time would you have to get out of the way? Answer in s.

2007-09-27 16:11:32 · 1 answers · asked by Anonymous

An inventive child wants to reach an apple in a tree without climbing the tree. Sitting in a chair connected to a rope that passes over a frictionless pulley (Fig. P4.79), the child pulls on the loose end of the rope with such a force that the spring scale reads 320 N. The child's true weight is 260 N, and the chair weighs 160 N.
Find the force the child exerts on the seat of the chair.

I know that the acceleration is 5.13 m/s^2 but how do I find the force the child exerts on the seat?? Thanks !

2007-09-27 15:47:04 · 1 answers · asked by me 1

A student throws a ball vertically upward such that it travels 6.40 m to its maximum height. If the ball is caught at the initial height 2.00 s after being thrown, answer the following.
(a) What is the ball's average speed?
wrong check mark m/s

(b) What is its average velocity?
wrong check mark m/s

2007-09-27 15:14:46 · 1 answers · asked by k 2

The drawing shows a baggage carousel at an airport. Your suitcase has not slid all the way down the slope and is going around at a constant speed on a circle (r = 11.8 m) as the carousel turns. The coefficient of static friction between the suitcase and the carousel is 0.760, and the angle in the drawing is 36.6°. How much time is required for your suitcase to go around once?

http://www.webassign.net/CJ/05_26.gif

2007-09-27 14:19:54 · 3 answers · asked by Alan W 2

as if they were the only mother effing class we have!! they load us up on homework they expect due the next damn day when we have five other teachers that do the same thing and they expect us to get it done on time?? what is wrong with them!!
please if your a teacher tell me because i really dont know why you do that.

2007-09-27 14:00:05 · 3 answers · asked by Anonymous

A 10-kg iron ball rolling at 2 m/s on a horizontal surface strikes a 1.0-kg wooden ball of the same size that is at rest. What is the speed of each ball after the collision? What proportion of the iron ball’s original KE was transferred to the wooden ball?

2007-09-27 13:26:55 · 1 answers · asked by miaka 1

like if your given a time and angle and have to find all other possible info.. whats difference between horizonta & vertical components??

2007-09-27 13:14:13 · 2 answers · asked by Anonymous

An object of mass 2kg travels east at 5m/s and crash in an object of 10kg traveling west at 1m/s.
A)What would be the final velocity if the objects stuck together?
B)What is the momentum of the 2kg object before the collision?
C)What is the total momentum after the collision?
D)Does this contradict the law of conservation of linear momentum?

2007-09-27 13:11:07 · 1 answers · asked by Anonymous