# Newton's Law of Universal Gravitation

1. Aug 9, 2010

### rvnt

1. The problem statement, all variables and given/known data
I am doing a lab-"Kepler's Laws and Newton's Law of Universal Gravitation". There is an image representing various positions, at equal intervals, of a satelitte in an elliptical orbit around the earth. A list of planets and their radi and periods are given. I have calculated acceleration using two formulas a=GMm/r^2 and a=4pi^2r/T^2
Question states: "Calculate acceleration using the two equations and compare the results. Do your results confirm Newton's law of universal gravitation?"

2. Relevant equations

F=Gm1m2/r^2
3. The attempt at a solution
Ex. of results: accleration obtained for Venus using 1st equation= 5.5407*10^24 and using 2nd equation=0.0113286

2. Aug 9, 2010

### thrill3rnit3

a=GMm/r^2 is wrong

go back to the general equation

F=Gm1m2/r^2
m1=mass of Venus
m2=mass of satellite

F=m2a=Gm1m2/r^2

a=Gm1/r^2

compare to the one you originally had (a=GMm/r^2)

3. Aug 13, 2010

### rvnt

But mass of the satellite isn't given..?

4. Aug 13, 2010

### rvnt

Wait...so as you said to use a=Gm1/r^2...for venus I got a=(6.67*10^-11)(4.8690*10^24)/(1.08*10^11)^2= 2.784*10^-8