# Need help find magnitude and angle displacement please!

1. Sep 7, 2009

### Darkhrse99

1. The problem statement, all variables and given/known data
A wheel with a radius of 45cm travels along a horizontal floor without slipping. At time T-1 the dot P painted on the rim is at the point of contact between the wheel and the floor.At the later time T-2 the wheel has gone through one half of a revolution. What are the magnitude an angle(relative to the floor) of the displacement of P?

3. The attempt at a solution

I believe the angle is 180* and the magnitude is 90cm. A half revolution is 180* and 2times 45cm is 90cm. Is this correct?

Thanks
Jason

Last edited: Sep 7, 2009
2. Sep 7, 2009

### HallsofIvy

Magnitude and angle of displacement of what? The center of the wheel has moved straight ahead. The angle of its displacement vector is 0. And it will have moved forward a distance equal to half the circumference of the wheel, not the diameter. Do you see why?

3. Sep 7, 2009

### Darkhrse99

The magnitude and displacement of P At t-0, P is at the bottom and t-2 P is at the top. Sorry I left that out of the question.

4. Sep 8, 2009

### Jebus_Chris

Draw a picture of the wheel at t-1 and at t-2 on the same axis. Then connect the two points and figure out the displacement+angle.