June 28, 2013

## What is the gravitational field strength on a satellite due to the earth?

Assuming that the satellite is 12000 km from the center of the earth, the earth weights 5.97 x10^24 kg, the distance of the satellite to the center of the earth is 1.20×10^5 km

Since you didn’t give the satellite mass, the force of attraction cant be calculated, but the acceleration of a low mass satellite can (approximately)
Ive taken the center to center distance (d) as 12,000 km = 12,000,000 meters (1.2e7 meters)
d = 1.2e7 meters
m1 = earth mass = 5.97e24 kg
m2 = satellite mass
G = newtons gravity constant = 6.673e-11

The equation for (total) acceleration of both bodies:
a = ( G * ( m1 + m2 ) ) / d²
But as the satellite mass makes little difference to the outcome provided it’s relatively small it can be ignored, leaving all the acceleration on the satellite and none on the earth (in theory):
a = ( G * m1 ) / d²
a = 2.768 (m/s)/s
So, for stable orbit, you must provide enough centripetal acceleration to balance this gravitational acceleration, by way of orbital velocity:
v = square root ( ( G * m1 ) / d )

actually, the equation for centripetal acceleration is: a = v² / d, you have a ( 2.768), so transpose
to feature v, then : v = square root ( a * d ), the answer is the same as above.

## How do I update anroid makret to google play on my phone?!?!?

I have a Sony Ericsson Xperia, I think its an X10. It’s one of the early Xperias, and its the sort of middleish sized one. I have tried googling how to get google play, but nothing has been of help!! I have connected my phone to my PC, and nothing happens, it just says its all up to date.

If you have a google account its just a whole different market. My tablet has like 2 or 3 different markets on it.

## How to calculate the cheek and cell size ?

Hi, I done a practical in my school and I need to know how to calculate a cell size. I’ve use a microscope thant magnified the cells by x4 x10 and x40
The cheek cell was x4 and it had 8 lines.(80 qm (field of view))
The onion cell was x10 and it had 18 lines (180 qm (field of view) )

Calculating Cell Size using microscope:
For details, visit :
http://72.14.235.132/search?q=cache:ygivLGvvhB0J:www.bisnet.or.id/vle/mod/resource/view.php%3Fid%3D5550+calculating+the+cheek+and+cell+size&hl=en&ct=clnk&cd=6&gl=in

## Outdoor Lighting and Music in the City?

I have a house in a major US City with a 3rd-floor outdoor deck that also allows access to the roof. These areas provide my only outdoor areas and excellent views of the city skyline, and thus are ideal for entertaining. The deck is small (about 10′ x10‘), has an outdoor light, and has one outlet. The roof has no electrical outlets or lighting. I am trying to find ways, preferably permanent, to light and provide music to these spaces. Also I am a college student on a very tight budget so the cheaper the better. Any and all suggestions are appreciated.

Dude,

Buy a whole bunch (bags) of these little white candles. Each is round, has it’s own aluminum base. We do this with our terrace…you can line then along edges of the balconey, ledges etc. Very Euro trendy and cheap. As for music…just get a smal techno “bro box”. You don’t need to blast loudly .

## How many seconds does it take for the signal to reach the Earth?

A space probe on the surface of Mars sends a radio signal back to the Earth, a distance of 9.51 x10^7 km. Radio waves travel at the speed of light (3.00 x10^8 m/s).

X = vt + (1/2)at^2;

x = 9.51 x 10^7 km = 9.51 x 10^10m
v = 3 x 10^8 m/s
a = 0

(9.51 x 10^10 m) = (3 x 10^8 m/s)t
t = (9.51 x 10^10 m) / (3 x 10^8 m/s)
t = 317s