Physics - March 2007

In Robert Heinlein's The Moon Is a Harsh Mistress, the colonial inhabitants of the moon threaten to launch rocks down onto the Earth if they are not given independence (or at least representation). Assuming that a rail gun could launch a rock of mass m at 2.90 times the lunar escape speed, calculate the speed of the rock as it enters the Earth's atmosphere.

_____km/h

2007-03-27 15:55:41 · 1 answers · asked by Justin A 1

If and object has a gravitational force of 5 Newtons but if air resistance is 0.5 Newtons what would be the net force?

2007-03-27 15:55:14 · 3 answers · asked by Anonymous

2007-03-27 15:52:56 · 3 answers · asked by manikant k 1

if an apple weighs 5Newtons and another weighs 10Newtons which apple has the greatest magnitude?
Thanks

2007-03-27 15:46:52 · 2 answers · asked by Anonymous

Is it he ground coming towards you or you going towards the ground?

2007-03-27 15:44:15 · 11 answers · asked by colin050659 6

Like a breach in a spacecraft?

How can I calculate the wind speed and rate of air loss moving through a hole, given the pressure differential, size of the hole, size of the air source, size of the air sink, temperature, etc.?

2007-03-27 15:42:55 · 2 answers · asked by anonymous 4

Also In a pulley system what is the output force and output distance?
I have a pretty good idea but just making sure.

2007-03-27 15:23:26 · 3 answers · asked by Jazz_Fingers 1

One possible means of achieving space flight is to place a perfectly reflecting aluminized sheet into Earth 's orbit and use the light from the Sun to push this solar sail. Suppose such a sail, of area 5.60 104 m2 and mass 6300 kg, is placed in orbit facing the Sun. Ignore all gravitational effects, and assume a solar intensity of 1380 W/m2. (Hint: The radiation pressure by a reflected wave is given by 2 (average power per area)/c.)
(a) What force is exerted on the sail?
F = N
(b) What is the sail's acceleration?
a = m/s2
(c) How long does it take for this sail to reach the Moon, 3.84 108 m away?
t = days

2007-03-27 15:16:29 · 1 answers · asked by joe p 1

The Sun delivers an average power of 0.9 W/m2 to the top of Pluto's atmosphere. Find the magnitudes of E max and B max for the electromagnetic waves at the top of the atmosphere.
B max = T
E max = V/m

2007-03-27 15:16:05 · 1 answers · asked by joe p 1

A transformer on a pole near a factory steps the voltage down from 3600 V (rms) to 120 V (rms). The transformer is to deliver 1000 kW to the factory at 94% efficiency. Find values for the following.
(a) the power delivered to the primary
kW
(b) the current in the primary
A
(c) the current in the secondary
A

2007-03-27 15:15:21 · 1 answers · asked by joe p 1

Well...this is somewhat hard to explain.
Imagine you were holding a cloth vertically. You then dip the bottom tip of the cloth into water. You will notice that the water travels from the bottom tip of the cloth, upwards.

My question is, how can this be? Wouldn't the force of gravity restrict the motion of the water, and pull it down? What force (or concept) allows this motion? If this is a force, Why does this force overcome gravity?

I know its a weird question...and its not for school or anything. I did about an hour of research, and even asked my physics teacher about this, and he couldn't provide me with a suitable scientific explanation.

Thx

2007-03-27 15:13:27 · 4 answers · asked by james 2

2007-03-27 15:10:32 · 4 answers · asked by m a 1

I took chemistry this year

2007-03-27 15:03:49 · 6 answers · asked by Laela06 2

Hello guys, I really need help with this physics problem. It has been bugging me for a while and I keep getting stuck. If you can't solve it, if you know where I can find a site that has solutions this would be a great help. Thanks!

A l.0 kilogram object is moving horizontally with a velocity of 10 meters per second, as shown above, when it makes a glancing collision with the lower end of a bar that was hanging vertically at rest before the collision. For the system consisting of the object and bar, linear momentum is not conserved in this collision, but kinetic energy is conserved. The bar, which has a length l of 1.2 meters and a mass m of 3.0 kilograms, is pivoted about the upper end. Immediately after the collision the object moves with speed v at an angle  relative to its original direction. The bar swings freely, and after the collision reaches a maximum angle of 90° to the vertical. The moment of inertia of the bar about the pivot is Ibar = ml²/3 Ignore friction.

2007-03-27 14:59:32 · 2 answers · asked by djibouti1989 1

A long uniform rod which weighs 5.00 X 10^2 N leans against a smooth vertical wall. It leans with an angle of 60.0 degrees with respect to the horizontal floor. The rod is 1.5 meters long.

a) Find the Normal Force exerted by the wall.
b) Find the horizontal and vertical components of the force exerted by the floor assuming the rod is in equilibrium.
c) If the rod begins sliding such that it has an angular acceleration of 3.1 rad/s^2, what will the net torque be? (The moment of inertia of the rod can be calculated using I= (1/3) ML^2.)

2007-03-27 14:39:37 · 2 answers · asked by LesJerLayne 2

2007-03-27 14:36:42 · 5 answers · asked by SHELLTOE BISCUITS 3

The Sun delivers an average power of 0.9 W/m2 to the top of Pluto's atmosphere. Find the magnitudes of E max and B max for the electromagnetic waves at the top of the atmosphere.
B max = T
E max = V/m

2007-03-27 14:22:55 · 1 answers · asked by asiansenz 1

Two speakers are driven by the same oscillator with frequency of 215 Hz. They are located 3.59 m apart on a vertical pole. A man really far away walks straight toward the lower speaker in a direction perpendicular to the pole. How far is he from the pole at the first moment he hears a minimum in sound intensity (short of infinity) if the speed on sound is 330 m/s?

Can anyone tell me how to get this one started?

2007-03-27 14:22:37 · 3 answers · asked by Nicole V 1

if period of revolution is doubled, what will be the effect on the centripetal force?

2007-03-27 14:19:52 · 2 answers · asked by Jane A 3

How far does the image of a car appear behind a convex mirror, with a focal length of -6.0 m, when the car os 10.0 m from the mirror?

Please help me with this problem.
I don't understand it.

2007-03-27 13:56:48 · 1 answers · asked by swimmertommy 1

I missed ap physics this morning and i'm not sure how to do this problem, any help would be awesome.

A mass m1= 30kg slides without friction on the horizontal surface being pulled by m2=80kg with a string over a frictionless pulley. The pulley is a thin cylindrical shell of mass M=10kg and radius R. The string turns the pulley without slipping. Find a) acceleration of each mass, b) the angular acceleration of the pulley, C) the tension in each part of the string.

2007-03-27 13:56:32 · 1 answers · asked by lpfanz89 1

Help with physics please?
I have no idea what to do here, any explanation would be great.

In the figure the large mass disk has mass 2 kg radius 0.2m and initial angular velocity 50 rad/sec and the small disk has mass 4kg radius 0.1m and initial angular velocity 200 rad/sec (about 1900 rpm). A) find the common final angular velocity after the disks are pushed into contact. B) Is kinetic energy conserved during this process.

2007-03-27 13:55:30 · 1 answers · asked by lpfanz89 1

what happens inside the light bulb when it is off, and what happens to the electrical current in the light bulb when it is turned on?

2007-03-27 13:41:52 · 3 answers · asked by iNeedhelp 4

I need to know if light bulbs are polar anyone know?

2007-03-27 13:40:39 · 1 answers · asked by Anonymous

Do the known theories of physics allow for free will without a multiverse(parallel worlds with different possibilities) to compensate for choice?

As in, is it all either pre-planned or make use of the multiverse, or are there any theories that allow for choice in a single non divisive universe?

2007-03-27 13:27:35 · 4 answers · asked by Luis 6

I am doing a science experiment for extra credit. Which would you choose??

1) Red
2) Blue
3) Green
4) Yellow

Explain why. Mybe a past memory or how it might describe yourself.

2007-03-27 12:38:42 · 13 answers · asked by bead_flea 1

When something explodes, say an atom bomb, what happens at the very core of it?

Not what causes the explosion, but right afterwards. Does it create a vacuum at it's core at the moment of explosion or does the core become very compact?

2007-03-27 12:29:27 · 6 answers · asked by Luis 6

The spheres are connected by a conducting wire. Find the electrostatic force between the two, after equilibrium is reached.

2007-03-27 12:11:17 · 2 answers · asked by Nate E 1

If a proton travels between two oppositely charged plates (that start from rest). And the proton hits the negative plate at a speed of 3.8 x 104 m/s. How would you find the potential difference between the plates?

2007-03-27 12:09:55 · 3 answers · asked by Question-er 2

2007-03-27 12:08:47 · 22 answers · asked by Anonymous