Physics - February 2007

Hi,

Consider the circuit in Figure P31.77 ( http://i137.photobucket.com/albums/q208/infinitbelt/p31-77alt.gif ), in which V = 90 V, R = 25 , and the switch has been closed for a very long time.


(a) What is the charge on the capacitor?

(b) The switch is opened at t = 0 s. At what time has the charge on the capacitor decreased to 10% of its initial value?


I tried finding the total resistance of the circuit, and I got 67.1. Then I used Q=VC to solve for Q but I am still not getting the right answer.



Thanks!

2007-02-19 15:36:35 · 3 answers · asked by Anonymous

everyone said that is we cannot use alkaline batteries in small devices. the main reason is that it is not economical to use it compare with normal carbon zinc batteries.

small devices such as clocks and remote controls draw little current, normal carbon zinc batteries will do as good as an alkaline battery. that means that if you install a alkaline battery (much more expensive than a normal carbon zinc battery) into a clock, they will have the same life as a carbon zinc battery.

2007-02-19 15:35:14 · 1 answers · asked by formystudies3 1

i saw a guy playing with tesla coils. he wore metal gloves and a metal helmet so he could spark from his metal rather than his skin, which could cause him to be burned or elctrocuted?

2007-02-19 15:32:39 · 5 answers · asked by Anonymous

Need help on science homework. Answer back quickly. Due tomorrow.

2007-02-19 15:17:35 · 3 answers · asked by Ted Lim 2

What eactly the chaos theory try to explain?

2007-02-19 15:14:55 · 10 answers · asked by Ayan 1

Suppose a baseball is shot up from the ground straight up with an initial velocity of 64 feet per second. A function can be created by expressing distance above the ground, s, as a function of time, t. This function is s = -16t2 + v0t + s0
•16 represents 1/2g, the gravitational pull due to gravity (measured in feet per second2).
•v0 is the initial velocity (how hard do you throw the object, measured in feet per second).
•s0 is the initial distance above ground (in feet). If you are standing on the ground, then s0 = 0.
a) What is the function that describes this problem?
Answer:
is the answer a parabola?

2007-02-19 15:10:29 · 4 answers · asked by Anonymous

2007-02-19 15:09:56 · 3 answers · asked by twinsterles 1

A 5 m long ladder weights 200N and rests against a smooth vertical wall with its base on a horizontal rough floor, with a coefficient of static firction of .2. The ladder is 1.3m away from the wall and the ladders center of mass is 2.5m from its base. How far up the ladder can a 600N person climb without falling?
Please help!

2007-02-19 14:57:40 · 1 answers · asked by bluevolleyball12 1

.
Assumption: The object is moving forward. The light is emitting from the front of the object.

2007-02-19 14:48:11 · 8 answers · asked by Chi Guy 5

i read a mesage on an eye chart that said something about viewing the chart at an angle of one minute (1/60th degrees). that makes no sense because of the infinitesimal size of one minute at a distance of a few feet.

2007-02-19 14:36:29 · 3 answers · asked by Anonymous

I am doing a worksheet for physics and I can't seem to answer this question:

If the wave frequency is great on one end, then it represents the deep end. If wave frequency is smaller on one end, it represents the shallow end. why?

2007-02-19 14:34:07 · 1 answers · asked by Anonymous

What is the current in a 5.09 ohm resistor connected to a battery that has a .1 ohm internal resistance when the potential drop across the terminals of the battery is 5 V? Answer in units of A

2007-02-19 14:27:22 · 1 answers · asked by jeremiah g 2

of 1 N on one another|?

2007-02-19 14:18:23 · 1 answers · asked by Anonymous

Mass of person is 70 kg...
ur on a bathroom scale in an elevator...
the elevator is moving down with an accerlation of 2.0 m/s^2

2007-02-19 14:13:45 · 1 answers · asked by no name 1

How is the work output of a machine related to its work input?
a)always less
b) always greater
c) always equal
d) always zero



The mechanical advantage of a pulley system depends on
a) the diameter of the pulley wheels
b) the length of the rope
c) the number of sections of rope
d) the direction of the input force

2007-02-19 14:12:33 · 2 answers · asked by maconheira 4

I don't understand this at all!
Can someone explain harmonics of a guitar?

Here is the first part of a problem I have for homework:

A high E string is 65 cm, and its frequency is 330Hz. When the first fret is pressed, the E becomes an F at 350Hz. What is the distance between to the fret?

2007-02-19 14:11:59 · 2 answers · asked by ☆ 2

A 200kg box is pulled at constant speed by the little engine pictured below. The box moves a distance of 2.5 m across a horizontal surface.How much energy is transfered by the engine

2007-02-19 13:54:14 · 1 answers · asked by w_xsoadx_w 2

2007-02-19 13:54:13 · 9 answers · asked by Anonymous

2007-02-19 13:50:49 · 2 answers · asked by Carlos 2

i need to calculate velocity fo a science experiemnt. if you need more info. ask me for it. i need answers ASAP!

2007-02-19 13:49:21 · 0 answers · asked by J 2

I was curious if there were any studies into taking radiation and converting it directly into electrical energy. My understanding of nuclear energy is that they are basically big steam engines. Is there a way to cut out the steam power and get the energy directly from radiation? Radiation is everywhere- the computer I'm writing on and even the table it's sitting on is giving off some radiation. It would be interesting to know more about this.

2007-02-19 13:40:08 · 4 answers · asked by Anonymous

A skier is pulled up a slope at a constant velocity by a tow bar. The slope is inclined at 20.6 ° with respect to the horizontal. The force applied to the skier by the tow bar is parallel to the slope. The skier's mass is 52.3 kg, and the coefficient of kinetic friction between the skis and the snow is 0.183. Find the magnitude of the force that the tow bar exerts on the skier.

2007-02-19 13:31:33 · 2 answers · asked by sweetbolbola 2

...or a hopeless pursuit?

2007-02-19 13:26:09 · 5 answers · asked by Anonymous

I understand that antimatter is matter that is oppositely charged than the matter that our planet is made of, and that antimatter destroys regular matter. Can any antimatter destroy any other regular matter, or does it have a specific opposite somewhere in the universe, and it will only destroy that specific particle? Please explain all you know.

2007-02-19 13:16:29 · 4 answers · asked by Anonymous

would it be easier to drive at a high speed around an unbanked horizontal curve on the moon than to drive around the same curve on earth?

2007-02-19 13:16:13 · 2 answers · asked by Anonymous

and the canonical ensembles.
averageE=kT^2(partial lnQ/partialT)N,v
average p=kT(partial lnQ/partial v)N,T
S=kT(partial lnQ/partialT)N,V +k lnQ

2007-02-19 13:10:51 · 1 answers · asked by zizi m 1

My friend and I are having a debate. I think that a can of diet coke weights less than a can of regular coke due to its chemical make-up (sugar content). However, she disagree's. We do not have access to a scale sensitive enough to weigh the two cans. Does anyone else have any accurate data, such as how much the two weigh?

2007-02-19 13:06:58 · 4 answers · asked by ArmyMomof 2 1

some one told me there was a 40 year light buld i want the longest lasting one they make something at least 10 years. if you can find a 40 year one all i want is links to page and price. i will give the points after i see the links.

2007-02-19 13:04:07 · 0 answers · asked by fred96002001 3

a diver runs horizontally off the end of a 5 m high drivng board at 6 m/s.
a) how long does it take for diver to hit water? is it 1.445 s?
b) how far horizontally does the diver end up from the board? i'm confused, isn't it 5 m?
c) what is size of horizontal component of the driver's velocity just before he hits the water? do I have enough info to construct one? how should it look like?
d) size of vertical y component velocity before he hits water?
e) speed in m/s? i guess size does not have direction, but how can it be differnt from its velocity?

2007-02-19 13:02:37 · 2 answers · asked by soccerjock 2

1) A 1550 kg car moves down a level highway under the actions of two forces: a 1070 N forward force exerted on the drive wheels by the road and a 1020 N resistive force. Use the work-energy theorem to find the speed of the car after it has moved a distance of 16 m, assuming that it starts from rest.
------------------------------------------------------
2) A skier of mass 63 kg is pulled up a slope by a motor-driven cable.
(a) How much work is required to pull him 85 m up a 30° slope (assumed frictionless) at a constant speed of 2.4 m/s?
___ J
(b) What power must a motor have to perform this task?
___ hp

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3) A block of mass 12.0 kg slides from rest down a frictionless 35.0° incline and is stopped by a strong spring with k = 3.00 104 N/m. The block slides 3.00 m from the point of release to the point where it comes to rest against the spring. When the block comes to rest, how far has the spring been compressed?
___ m

2007-02-19 13:02:05 · 1 answers · asked by Anonymous