# Homework Help: Build a clock

1. Oct 30, 2006

### hatingphysics

1) The earth rotates once per day about its axis. Where on the earth's surface should you stand in order to have the smallest possible tangential speed?

would it be on the top of axis since it will not move?

2) It is possible, but not very practical, to build a clock in which the tips of the second hand, the minute hand, and the hour hand move with the same tangential speed. Explain why it would be possible but not practical.

I have no idea here....i didn't even know this was possible?!

3) Suppose that the speedometer of a truck is set to read the linear speed of the truck, but uses a device that actually measure the angular speed of the tires. If larger diameter tires are mounted on the truck, will the reading of the speedometer be correct? if not, will the reading be greater than or less than the true linear speed of the truck? Why?

No, because the diameter is more for the wheel which will give a larger speed compared to the linear speed. Is this true....i don't know what the right answer is.

4) The blades of a fan rotate more and more slowly after the fan is shut off. Eventually they stop rotating altogether. In such a situation we sometimes assume that the angular acceleration of the blades is constant and apply the equations of rotational kinematics as an approximation. Explain why the angular acceleration can never really be constant in this kind of situation.

is it because the speed of the fan turning off is changing till it stops?

5) Rolling motion is one example that involves rotation about an axis that is not fixed. Give three other examples. In each case, identify the axis of rotation and explain why it is not fixed.

i have no clue!

Last edited: Oct 30, 2006
2. Oct 30, 2006

### Hootenanny

Staff Emeritus
One is expected to show one's own efforts before requesting help.

3. Oct 30, 2006

### geoffjb

Think of the length of each hand.