# Homework Help: Gravity of the sun

1. Oct 17, 2004

### guru

What is the acceleration due to gravity of the sun at the distance of the earth's orbit?

i have no idea where to begin.
Help

2. Oct 17, 2004

### Tide

The gravitational pull of the Sun on the Earth is the centripetal force keeping the Earth from flying off into the great beyond.

3. Oct 17, 2004

### geometer

Find the mass of the sun, and the distance between the sun and the earth. Then, think about Newton's Law of Universal Gravitation.

4. Oct 17, 2004

### guru

This is what i obtained
Sun's Mass: 1.99x10^30 kg,
earth-sun distance: 150x10^6 km.

law of gravitional = Gm/r^2
G=6.67*10^(-11)

((6.67*10^(-11)) * (1.99*10^30))/ (2.25*10^12)

is that right?

Last edited: Oct 17, 2004
5. Oct 17, 2004

### pervect

Staff Emeritus
Probably the simplest and most direct approach is to use Newton's law of gravity.

Do you know what that is?

6. Oct 17, 2004

### guru

law of gravity = Gm/r^2
G=6.67*10^(-11)

((6.67*10^(-11)) * (1.99*10^30))/ (2.25*10^12)
right?

7. Oct 17, 2004

### Tide

The acceleration due to the Sun's gravity at the location of the Earth is just

$$a = \frac {v^2}{R}$$

where v is the speed of the Earth around the Sun and R is the radius of Earth's orbit. You know R and you know the Earth travels a distance of $2\pi R$ in one year so you know its speed too.

8. Oct 18, 2004

### geometer

That should be right!