# Mass and gravity HELP PLEASE

1. Mar 12, 2005

### mushhhy

I hope this is in the proper section, if not sorry.
I need help understanding therelationships between gramass and gravity
masss is m weight is w gravity is g m=w/g, if w is expressed in kg and g in (m/s^2) the resultant will be in newtons. Is this right or wrong ?

If I am trying to obtain the force F exerted on an object (in newtons) and the mass is expressed in newtons and multiplied by the acceleration in (m/s^2) will the answer still be in newtons ?

Please explain this process to me

2. Mar 13, 2005

### Staff: Mentor

I'm not exactly sure what you are trying to do, but I'll make a few comments. An object has mass, which is measured in kg. The object's weight is the gravitational force exerted on it. Force is measured in Newtons. For an object on the earth's surface, the weight equals mg, where "g" is the "acceleration due to gravity", which is about 9.8 m/s^2. Thus: w = mg.

All of this relates to Newton's 2nd law: F = ma, in which force has units of Newton, mass has units of kg, and acceleration has units of m/s^2. (Note that this is just one common system of units; there are others.)

3. Mar 13, 2005

### mushhhy

Thanks, can you help with my other posts

4. Mar 15, 2005

### tony873004

This might be a cruel lesson in units if you meant that the mass was expressed in Newtons divided by the acceleration, instead of Newtons multiplied by the acceleration.

F=ma, therefore, m=F/a, and units for m could be N/m/s^2.

I have a book that is 2 kg.
I have a book that is 2 N/(m/s^2)

They are the same thing, but people will look at you funny if you express it the 2nd way.

And if this is what they meant, yes, the resulting force will be in Newtons.