# Homework Help: Free body diagram (centripetal force)

1. Oct 22, 2008

### dnt

1. The problem statement, all variables and given/known data

simple question really - how do you draw the free body diagram for a car going around a corner?

2. Relevant equations

n/a

3. The attempt at a solution

i know the net force, the centripetal force, points towards the middle. i have an engine force pointing tangentally outwards...where is the missing force? is it friction? and when i try to figure out its direction i have it pointing between the engine force and centripetal force but that doesnt make sense if its friction.

am i on the right path? does this make sense so far?

2. Oct 22, 2008

### Redbelly98

Staff Emeritus
Yes, friction is definitely present.

Engine force usually isn't needed, but it's direction would be to accelerate the car forward.

How about forces in the vertical direction?

3. Oct 22, 2008

### dnt

forces vertically would be weight and normal i think.

im trying to draw my diagram from a birds eye view. and i cant figure out which way friction would point or if there is another force too. my logic is that if there is a forward force (engine force?) there would have to be at least one other force such taht those vectors add up to the centripetal force (which is perpendicular to the engine force and points towards the center of the circle).

4. Oct 22, 2008

### fredrick08

friction should be directly opposite to the engine force right?

5. Oct 22, 2008

### dnt

yes but then how do those add up to the centripetal force? on the diagram it doesnt add up

6. Oct 22, 2008

### Redbelly98

Staff Emeritus
Centripetal force is a net force on the car, it is caused by one or more of the other forces that have been mentioned.

7. Oct 22, 2008

### dnt

but i thought the sum of all the forces has to equal the net force (ie, centripetal force) - how come on my diagram those force vectors dont add up to the centripetal force vector?