# Force Diagram

1. Jun 11, 2008

### forty

(a) Assume that the Earth is a uniform sphere with a radius r which rotates such that the speed of the ground at the equator is v which is constant.

(i) Draw a diagram showing the forces acting on a person standing on the equator.

There would be the following forces acting on the person:

Gravity (mg)
Normal (-mg)
Friction at the point of contact to the earth
Centripetal force (?)

(ii) Explain why a person in this situation must experience a net force even though their speed is constant.

Does this have to do with the centripetal force? So they need to have a net force towards the center of the earth??

Any help with these would be greatly appreciated.

2. Jun 11, 2008

### CompuChip

Since you are talking about force diagrams, I assume you know about vectors. In (ii) the question says that $|\vec v|$ is constant, but is $\vec v$ constant as well?

3. Jun 11, 2008

### forty

so the magnitude of v is constant but the direction is changing hence you are accelerating and if you are accelerating your are experiencing a net force?

4. Jun 11, 2008

### Staff: Mentor

Absolutely. So redo your analysis of the forces acting on the person.