# Homework Help: Force/Newtons law Q help

1. Jan 9, 2013

### pencilcase

A cyclist is pedaling so that a force of 100N pushes her forward while there are 50N of friction and 50 N of air resistance opposing her movement. What is the net force on the cyclist?

2. Jan 9, 2013

### Dick

Sounds pretty easy to me. What do you think? That's the important part.

3. Jan 9, 2013

### pencilcase

i think its either 200n or 0n :/

4. Jan 9, 2013

### Dick

That's good. So which? 100N forward. I think 'opposing her movement' should tell you which direction the other two are, yes? 'Net force' means you add the forces considering the sign of each one.

5. Jan 9, 2013

so its 200 n

6. Jan 9, 2013

### Dick

Right. If she's moving 20km/hr she'll keep on moving 20km/hr until she stops working and slows down or works harder and speeds up.

7. Jan 9, 2013

### Dick

I liked your first answer better. If you call forward positive then the other backward forces are negative. 100N+(-50N)+(-50N)=0N.

8. Jan 9, 2013

### pencilcase

ooooooh ok thanksss!!!!!