Physics - February 2007

i have a problem in electrics in physics:

a dry battery of emf=3.0 volts supplies current thru a circuit in which the resistance can be changed. a high resistance voltmeter is connected across the bettery. as the current in the circuit is increased,the voltmeter reading decreases.explain this....


i cannot get that if the current increases(meaning the resistance must have been decreased), then why does the voltage increase?...i mean voltage is fixed,isnt it?

2007-02-19 20:28:42 · 6 answers · asked by catty 4

2007-02-19 19:12:43 · 5 answers · asked by clars 1

Is it possible for an object to have a system that has linear momentum but no kinetic energy? Can it have kinetic energy without linear momentum? Explain.

2007-02-19 19:09:03 · 3 answers · asked by clara y 1

Explain why a rocket can accelerate even in outer space, where there is no air against which it can push.

2007-02-19 19:05:53 · 4 answers · asked by clara y 1

Why, when you release an inflated untied balloon, does it shoots off into the air? Would the same thing happen if the balloon were released in a vacuum?

2007-02-19 19:01:47 · 2 answers · asked by clara y 1

2007-02-19 18:57:19 · 2 answers · asked by clara y 1

2007-02-19 18:56:45 · 8 answers · asked by clara y 1

2007-02-19 18:55:06 · 2 answers · asked by clara y 1

If d=at2/2 finds the distance but I don't have the time or velocity but I do have the acceleration and distance, would using Squareroot 2d/a=t be the correct equation to use to find time?

2007-02-19 18:45:46 · 2 answers · asked by pacific_crush 3

Information that can help answer;
a. who invented the movie soundtrack?
b. the history of its development
c. the physics of how it works

etc.

2007-02-19 18:36:44 · 1 answers · asked by Anonymous

Just to get the juices flowing:

1)Discuss the advantages of Helmholtz coils as a provider of uniform field. How much current would it take to provide a region in which the Earth's field was canceled for coils of 1.0-m diameter with 200 turns each?

2) An electron of mass 9.11e-31 kg travels in a circular orbit within a large evacuated chamber. The orbit has a 3.0 mm radius and is perpendicular to a B-field of 0.070 T. What's the electron's speed?

3) A 1.70 m long straight wire experiences a maximum force of 1.90 N when in a uniform 1.340 T B field. What current must be passing through it? [Hint: Maximum force occurs when = 90°.]

2007-02-19 18:30:48 · 1 answers · asked by Jake D 2

i got answers for this question yesterday, i just want to make sure I can solve them right so tell me if what im doing seems correct. And if you correct me try to solve it using one of these formulas:

V=at+V0
(X-X0)= 1/2 (V+V0)t
V^2=V0^2 + 2a (X-X0)
X-X0 = 1/2at^2 + V0t

now...check and see if what I say sounds good

A ball is thrown vertically upward with a velocity of +10.0 m/s.
(a) How high does it rise?
___m

Using V^2=V0^2 + 2a (X-X0)
10^2=0^2 + 2 * 9.8 *x, x = 5.10m

(b) How long does it take to reach its highest point?
___s

Using V=at+V0

10=9.8x, x= 1.0204sec

(c) How long does the ball take to hit the ground after it reaches its highest point?
___s

Heres where I get a bit confused, which equation should I use for this? Would the answer be the exact same? or would it be different a little? I know its pretty much 1 sec

(d) What is its velocity when it returns to the level from which it started?
___m/s

Also help with this one please, I think its just 9.8, thanks

2007-02-19 18:30:34 · 3 answers · asked by Anonymous

2007-02-19 18:30:17 · 5 answers · asked by Anonymous

I cannot understand this problem. Please help me :( I would appreciate it a lot. Thank you much.

Three objects with mases, m1 = 5.0 kg, m2 = 10.0 kg, and m3 = 15.0 kg, are attached by strings over frictionless pulleys as indicated in the figure linked below. The horizontal surface is frictionless and the system is released from rest. Using energy concepts, find the speed of m3 after it moves down 4.0 m.

http://www.webassign.net/sf/p5_32.gif

2007-02-19 18:00:20 · 2 answers · asked by Hotaru 1

Two massless springs with spring constants k1=4.0N/m and k2 = 6.0 N/m are welded together at point A. A mass m = 1.0 kg that slides along the frictionless surface is incident on the springs with a velocity of V0 = .5 m/s. It hits a massless plate with velcro on the end of spring 2 and sticks.
a) In terms of k1 and k2 what is the effective spring constant keff characterizing the system, i.e. what is the spring constant of the single spring that could replace these two and give the same motion of the mass?
b)What is the maximum compression Xmax that the mass reaches from the initial equilibrium length of the springs?

The diagram has the mass sliding towards the springs where it would hit spring 2 which is joined to spring 1 at point A, with spring 1 attached to the wall.

2007-02-19 17:48:07 · 2 answers · asked by Jeff 2

Forces of Magnitude of 250 pounds and 130 pounds act on an object at angles 45 degrees and negative 60 degrees, respectively, with the x axis. Find the direction and magnitude of the resultant of these forces

2007-02-19 17:42:51 · 2 answers · asked by leonard 1

My sister's in her first year of college. She tried to take biology, but on her 1st day, the teacher explained to the class that if they hadn't already taken chemistry, they would have a ruff time in her biology class. My sister dropped the class a week later due to complete confusion. She then attempted chemistry, but also ended up dropping out of it within the 1st week since she never took chemistry or physics in high school; and doesn't even understand what an atom is! Yes, the school system has failed her, what to do now? I found that physics, since it's the basis for understanding the more abstract concepts introduced in chemistry and biology, would be the best starting point for her. But, physics (along with all sciences) requires lots of math. My sister's taking college algebra right now. My question is, what math courses/subjects are recommended to take/learn before taking a college physics course (assuming no prior chemistry or biology courses have been taken)? thanks

2007-02-19 17:33:15 · 2 answers · asked by World Expert 1

Expain the pancake theory and why the floors didn't slow down exponentially as one hit the other.

2007-02-19 17:17:51 · 6 answers · asked by Anonymous

uniform beam weighing 254N stucks out from a vertical wall.
lightweight cable connects the end of the beam to the wall, making an angle of 65 between the beam and the cable.

Plz dont just give answers, show how you did it
thank you in advance

2007-02-19 17:09:39 · 1 answers · asked by Anonymous

if we filll a tank with equal quantity of Hydrogen and Oxygen , which one will get rapidly leak ?

2007-02-19 17:07:15 · 3 answers · asked by dhannya G 1

Did in this case, vol. of displaced water= weight of displaced body, obeyed?

2007-02-19 17:01:23 · 10 answers · asked by PearL 4

W/out working in the science field?

2007-02-19 17:00:57 · 6 answers · asked by Em 2

2007-02-19 16:48:35 · 3 answers · asked by Anonymous

I'm writing a SF story, and I need to be able to have clouds of gas persist in interplanetary space without them dissapating. I'll also occasionally want these clouds to 'drift' into and out of planetary orbits, infecting the atmospheres.

I've thought of and rejected electromagnetism, because that would probably ionise the gas, which I don't want, and as I understand it, gravity would not be strong enough to hold gas particles together. Any ideas?

2007-02-19 16:44:33 · 4 answers · asked by dead_elves 3

There has to be a vast difference because when my cast iron stove is cold, it takes a long time to warm up. If it is even slightly warm from a previous fire it heats very quickly. The question I suppose I should be asking is how does heat as a form of radiation move through solid objects. Like the sun? Protons and neutrons bouncing around forever before they reach the surface?

2007-02-19 16:37:13 · 2 answers · asked by brokolay 3

2007-02-19 16:15:28 · 3 answers · asked by BHUSHIT V 1

1. What is having too many amps in a circuit called? (starts with an O)
2. What is something that allows electricity to flow easier?
3. What is a drop in voltage due to great distance electricity travels along a wire (2 words)
4. Has the same current throughout?
5. Has same voltage in each branch?
6. How would you place a negative charge on an electroscope?
7. What happens at the zinc and copper terminals of a wet cell?
If you could answer any of these, that would be FANTASTIC!
Thanks!

2007-02-19 16:06:31 · 3 answers · asked by JJ 1

I think I can pretty much figure this out except one important detail that I don't know how to include: the angle of the face of the putter.

mass of putter (m1): .1325kg
initial velocity of putter (v1): 1.253 m/s
Angle of face of putter: 3 degrees
mass of golf ball (m2): .0047kg
initial velocity of golf ball (v2): 0

I'm pretty sure I need to solve for v1(final) and v2(final) in this formula:

Conservation of Momentum: m1v1 + m2v2 = m1v1(final) + m2v2(final)

Then plug them into the Energy Conservation formula to find the velocity of v2(final)...

Energy conservation: (.5)m1v1^2 + (.5)m2v2^2 = (.5)m1v1(final)^2 + m2v2(final)^2

....but, I have no idea where, when, or how to account for the angle of the putter.....not all the energy from the putter is directed into the horizontal motion of the golf ball.

If anyone can help, I'd so greatly appreciate it. I've been working on this forever.

2007-02-19 15:53:57 · 1 answers · asked by travo 1

An object of mass m is traveling on a horizontal surface. There is a coefficient of kinetic friction mu between the object and the surfaace. The object has speed v when it reaches x = 0 and encounters a spring. The object compresses the spring, stops, and then recoils and travels in the opposite direction. When the object reaches x = 0 on its return trip, it stops.

Find k, the spring constant.

Express k in terms of mu, m, g, and v.

Thanks in advance for the help!

2007-02-19 15:46:32 · 2 answers · asked by Amanda 2

A 250kg crate is placed on an adjustable inclined plane. If the crate slides down the incline with an acceleration of 0.7m/s^2 when the incline angle is 25 degrees, then what should the incline angle be for the crate to slide down the plane at constant speed?

2007-02-19 15:38:50 · 1 answers · asked by sfaulks89 1