# Homework Help: Newton Law problems

1. Nov 11, 2006

### rottentreats64

An applied force of 50 N is used to accelerate an object to the right across a frictional surface. The object encounters 10 N of friction. Use the diagram to determine the normal force, the net force, the mass, and the acceleration of the object. (Neglect air resistance.)
this is the image she gave us: http://faculty.xavierhs.org/wertkins/ipcf1113_files/image001.gif [Broken]

The picture is what is throwing me off, i thought the normal force would be what the object was actually moving at so 50n-10n= 40n. But i dont know what a net force is. I think the force of the object downward is how much it weighs so (w=m*g) 80=m*10 m=8 kg. Also to find the acceleration i dun know to use the normal force or net force in A=f/m

Last edited by a moderator: May 2, 2017
2. Nov 11, 2006

### physics girl phd

Double check your definitions. The net force is the sum of all ther forces on the object. The normal force is between the object and the surface.

I think your instructor is trying to teach you to the basics of drawing and using free-body diagrams.... you might want to look up so websites on that technique, or maybe there's a good tutorial on this site.

3. Nov 11, 2006

Also, note that the direction of the net force is the same as the direction of the acceleration.

4. Nov 11, 2006

### xAxis

The object will move according to F=ma, where F is the sum of all the forces acting on it, m=8kg as you've already found, and a is an acceleration of the object, which is in the direction of F.

5. Nov 11, 2006

### rottentreats64

The normal force is the same as the gravitational force, so Fnorm= 80N. Then I found out the mass by using the formula M=w/gàM=80n/10, the mass is 8kg. Then to find the net force you just do 50n (Fapp) – 10 N (Ffric) and you find out the net force is 40N. Then with this I was able to find the acceleration by using A=f/màA=40n/8, the acceleration is 5 m/s2.

6. Nov 11, 2006

### rottentreats64

is that right?

7. Nov 11, 2006