Physics - October 2007

A fireman 50.0 m away from a burning building directs a stream of water from a ground-level fire hose at an angle of 30.00 above the horizontal. If the speed of the stream as it leaves the hose is 40.0 m/s, at what height will the stream of water strike the building?

2007-10-15 00:08:35 · 1 answers · asked by slvrapple 2

1. Why positive charge moves from higher voltage to lower voltage?
2. why negative charge moves from lower voltage to higher voltage?
3. if one positive charge of 1 coulomb spontaneseously moves between point 100 volt and 150 volt, it converts some of the energy it has into energy of motion, how much energy would this charge convert to energy of motion?
4. 12 volts with 2 amperes and a circuit of 12 volt with 5 amperes, which has higher electrical resistance? why? (i answer the 2 amperes with higher resistance between with resistance, that's why it is lower or else with lower resistance, it would be 5 amperes)
5. why some magnetic materials are magnets while others are not but behave like one in the presence of another magnet?
6. why some materials are magnetic while others may be non-magnetic.?
7. if i drop a magnet through long vertical copper pipe and it moves slowly compared with the drop of a nonmagnetized object. why?
thx 4 the help, those were only problem i got stuck wit

2007-10-14 22:06:21 · 2 answers · asked by -- 1

i have a recitation tomorrow and i want to make sure I know what i am doing

http://class.phys.psu.edu/212Recitations/07_Circuits/DC_Circuits.pdf

ok in exercise 1, i figured the order should be B,A,C,D

i dont know if i'm right, but wouldn't less resistance mean more power? so less resistors equal more power? and parallel resistors would yield more power than resistors in a series?


part b of exercise 1


would the order be the same as well?

part2
I have no idea, i need help on this one.

2007-10-14 21:04:28 · 1 answers · asked by Anonymous

i need help w/ Lab exercise 2

http://class.phys.psu.edu/212Recitations/07_Circuits/DC_Circuits.pdf

2007-10-14 20:59:35 · 1 answers · asked by Anonymous

Compute the force (in Newtons) exerted by the water against either end of the pool. Do not include the force due to air pressure.

2007-10-14 20:49:32 · 1 answers · asked by Paul C 1

I understand that the Michelson-Morley result supports Einstein's first postulate and I understand how this postulate suggests such relativistic phenomena as time dilation and length contraction, but I read that Einstein was unaware of the Michelson-Morley result at the time of his theory's publication. So, what DID lead him to postulate the constancy of the velocity of light in vacuo???

2007-10-14 20:39:27 · 3 answers · asked by PhotonMan6.022 1

A hot-air balloon stays aloft because hot air is less dense than cooler air at the same pressure. Suppose the volume of such a balloon is 500 m^3 and its mass (in addition to the mass of the hot air) is 290 kg. The surrounding air is at 14.0 C. At this temp the density of air is 1.23 kg./m^3. The pressure inside and outside the balloon is the same.

What is the density of hot air in the balloon if it hovers in equilibrium?

What is the Celsius temp of hot air in the balloon?

Please explain and show your work, so that I may understand.

2007-10-14 19:13:56 · 1 answers · asked by nita 1

A falling stone takes 0.30 s to travel past a window 2.2 m tall. From what height above the top of the window did the stone fall?

PLEASE show all calculations. thanks a bunch.

2007-10-14 19:02:35 · 3 answers · asked by cc 2

Consider two particles A and B. The angular position of particle A, with constant angular acceleration, depends on time according to theta(t)=theta_0+omega_0t+0.5alpha t^2. At time t=t_1, particle B, which also undergoes constant angular accelaration, has twice the angular acceleration, half the angular velocity, and the same angular position that particle A had at time t=0.
How long after the time t_1 does the angular velocity of B have to be to equal A's?
___
ok, here we go:
i know that i have to write expressions for the angular velocity of A and B as functions of time, and solve for t-t1???
For A, omega(t) = omega_0 + alpha(t) and
for B, omega(t) = 0.5 omega_0 + 2alpha(t-t_1)
so when i equate them and solve for t-t_1, i get something that is not the right answer!

please help :(

2007-10-14 19:00:38 · 2 answers · asked by jaded20 1

Please explain the hard science, but also show the philosophical impacts and imaginative possibilities in laymen's terms. 10 points to the most complete yet user-friendly and imaginative answer.

2007-10-14 18:32:30 · 5 answers · asked by SPQRCLAUDIUS 2

2007-10-14 17:17:40 · 6 answers · asked by cc 2

2007-10-14 17:07:10 · 2 answers · asked by Mr Booo 2

magnetic line of force

2007-10-14 17:05:58 · 3 answers · asked by tata 1

Here is the LED
http://www.lsdiodes.com/shop/index.php?main_page=product_info&products_id=28

and here is the list of available resistors
http://www.lsdiodes.com/shop/index.php?main_page=product_info&cPath=10&products_id=68

I guess while we're talking about circuits, does anyone have an affordable soldering iron that they could recommend.

Thanks!

2007-10-14 16:53:41 · 1 answers · asked by X6B7A 2

this is the problem...q=2.5x10^-6 moving 500m/s in direction 30degNoE. At location of particle, B=0.4T. Particle experiences instantaneous magnetic Force due to field, F= 1.71x10^-4 N at 60degWoN. What is the size of the angle between the velocity vector and the magnetic field at the location of the particle? What is the direction of magnetic field? I don't know what to do. I am starting with finding the vector components. Is the 500m/s the "r" value for the velocity vector? I'm stuck there. If I start with components of force vector, how can I tell which components of velocity vector are perpendicular to the Force and B vectors. Do I include all vector components in the cross product, or just the perpendicular components? Please help me.

2007-10-14 16:37:41 · 1 answers · asked by Stephanie L 1

a 50.5 kg traffic light hangs from two cables which are at the angles shown.Calculate the tensions in the two cables.
http://i219.photobucket.com/albums/cc83/melan520/10-14-07_1249.jpg

2007-10-14 16:26:42 · 1 answers · asked by ? 2

how can you find the wavelength of a longitudinal wave

2007-10-14 16:20:38 · 3 answers · asked by lzp93627 1

A certain pendulum swings through an arc of one degree in one second. Next, the same pendulum is made to swing through an arc of two degrees. The time required to swing through the two-degree arc is:

a) one-half second
b) one second
c) two seconds

2007-10-14 15:57:24 · 3 answers · asked by ? 6

2007-10-14 15:03:28 · 3 answers · asked by nancy c 1

I've been reading up on Intelligent falling and in the research I've done, I have yet to find a way to prove this scientific theory wrong.

Are you certain God isn't the source of gravity as opposed to a massive object being the cause? Provide any evidence you may have.

2007-10-14 14:50:28 · 4 answers · asked by Wire Tapped 6

The length of a simple pendulum is 0.94 m and the mass of the particle )the Bob) at the end of the cable is 0.77 kg. The pendulum is pulled away from its equilibrium position by an angle of 8.6 degrees and released from rest. Assume that friction can be neglected and that the resulting oscillatory motion is simple harmonic motion.
A) What is the angular frequency of the motion
B) Using the position of the bob at its lowest point as the reference level, determine the total mechanical energy of the pendulum as it swings back and forth.
C) What is the bob's speed as it passes through the lowest point of the swing

2007-10-14 14:49:49 · 1 answers · asked by Anonymous

If a man stood in a large container which was on a scale and the scale showed that the total weight of the container and the man was 250 pounds (the man weighs 175 pounds) .....what weight would register on the scale while the man jumped up in the air? (during the time he was up in the air). Please explain your answer.

2007-10-14 14:39:45 · 6 answers · asked by me 1

A galvanometer with a coil resistance of 11.0 and a full-scale current of 0.160 mA is used with a shunt resistor to make an ammeter. The ammeter registers a maximum current of 4.00 mA. Find the equivalent resistance of the ammeter. ____ Ohms

2007-10-14 14:39:13 · 3 answers · asked by Hera08 1

In terms of thermal expansion, why is it important that a key and its lock be made of the same or similar materials?

2007-10-14 14:32:37 · 1 answers · asked by nancy c 1

A spring with spring constant k = 60 N/m and unstretched length of L0 is attached to the ceiling. A block of mass m = 1 kg is now hung on the end of the spring and is gently lowered.

a) How far does the spring stretch?

A chemistry student now pulls the block down until the total amount the spring is stretched is twice the amount found in part (a).
b) Assuming the mechanical energy of the block to be zero when the spring is in its unstretched position, what is the potential energy of the block when it is held in this new position?

c) What is the total mechanical energy of the block when it is this new position?

The block is now released and pushed upward with an initial speed vi = 2 m/s. d) What is the maximum speed of the block?

pic: https://wug-s.physics.uiuc.edu/cgi/courses/shell/common/showme.pl?cc/DuPage/Phys1201/fall/homework/Ch-08-Energy-Conservation/mass_vertical_spring/vertical-spring.jpg

2007-10-14 14:00:09 · 2 answers · asked by Anonymous

Two blocks are attached to each other. The mass of the first block is 80.0kg and its density is 1071 kg/m^3. The density of the second block is 120 kg/m ^3.

What is the volume of the second block if the arragement is barely afloat in water?

2007-10-14 13:52:45 · 1 answers · asked by Anonymous

An airplain is flying at 240m/s at an angle of 30 degrees with the horizontal. when the altitude of the plane is 2.4km, a flare is realiease. the flare hits the target on the ground, wat is the angle?

How do i even approach this i feel as if there isn't enough info

From a 60m cliff a rocket is launched upwards with Vo = 23 m/s at an angle of 50 degrees with respect to the horizontal. At what point above the ground does the rocket strike the wall of a vertical cliff located 20m away?

2007-10-14 13:48:30 · 1 answers · asked by Anonymous

An ideal gas is confined in a cylinder at 20 C and a pressure of 4 atm.

1. If the cylinder is surrounded by boiling water and allowed to come to equilibrium, what will the pressure of the gas be?

2. If the gas is allowed to escape until the pressure again reaches 4.0 atm, what fraction of the original gas, by weight, will escape?

3. If the temperature of the remaining gas now returns to 20 C, what is its pressure?

I'm so lost, please explain and show your work so that I may follow.

2007-10-14 13:48:22 · 1 answers · asked by Anonymous

A 4.5 kg block slides down a frictionless incline
making an angle of 31degrees with the horizontal.
The acceleration of gravity is 9.81 m/s^2
a) Find the work done by the gravitational
force when the block slides 4.1 m (measured
along the incline). Answer in units of J

b) What is the total work done on the block?
Answer in units of J.

c) What is the speed of the block after it has moved 4:1 m if it starts from rest? Answer in
units of m/s.

d) What is its speed after 4.1 m if it starts
with an initial speed of 1.4 m/s? Answer in
units of m/s.

I know it seems like a lot - I'm not asking for answers, just a little guidance on what equations to use - I'm sure i can figureit out then... Thanks so much!

2007-10-14 13:47:41 · 1 answers · asked by Anonymous

A firecracker is tossed straight up into the air. It explodes into three pieces of equal mass just as it reaches the highest point. Two pieces move off at 120 m/s at right angles to each other. How fast is the third piece moving?

2007-10-14 13:46:28 · 1 answers · asked by Jerry M 1