Homework Help: The gravitational force between the earth and a 2.600-kg mass on the surface of the e

1. Oct 16, 2009

Cloudy789

1. The problem statement, all variables and given/known data
Calculate the magnitude of the gravitational force between the earth and a 2.600-kg mass on the surface of the earth. The distance to the center of the earth from the surface is 6370 km and the mass of the earth is 5.98e+24 kg. HINT: This problem should take you about 5 seconds to solve. If you use G to answer this problem, you are not thinking.

M object = 2.6 kg
M earth = 5.98 X10+24
G constant = 9.81 m/s^2
Distance between masses = 6,370,000 m

2. Relevant equations
F = G[(M1*M2)/r^2)]

3. The attempt at a solution
9.81[(2.6*5.98e+24)/(6,370,000^2)]
9.81[(1.5548e+25)/(4.05769e+13)]
9.81(3.832e+11)
3.7589e+12 N

Yet, Capa says this is wrong and I can't think of another way to do this. Especially not without the G Constant.

2. Oct 16, 2009

Pengwuino

Re: The gravitational force between the earth and a 2.600-kg mass on the surface of t

This should take 5 seconds to solve as the problem stated.

F = ma

What is a? When one says F = mg, where g is the gravitational acceleration, what is the force acting upon?

3. Oct 16, 2009

Cloudy789

Re: The gravitational force between the earth and a 2.600-kg mass on the surface of t

Wow... I am truly an idiot.
Thank you.

4. Mar 3, 2011

stsraz

Re: The gravitational force between the earth and a 2.600-kg mass on the surface of t

Ok, so I'm working on the same problem and feel like a complete moron because I don't see what you're getting at... could someone give me a bit more information so I can understand where this problem is heading... thanks.