- #1

mvrk10256

- 2

- 0

This is my first post here so please be gentle if I did anything wrong. Also this is for Emag class and its a 4000 level class but this question seems better suited for this forum. I have been doing homework all day and I do not knwo if I am just tired, but I cant get this.

Work this problem in both Cartesian (rectangular) coordinates and plane polar coordinates:

Consider an analog watch that keeps perfect time and assume the origin to be at the center of the dial, the x axis passing through the 12 mark, and the y axis passing through the 3 mark.

(a) Write the expression for the time-varying unit vector directed along the hour hand of the watch.

(b) Write the expression for the time-varying unit vector directed along the minute hand of the watch.

(c) Obtain the speciﬁc expression for these unit vectors when the hour hand and the minute hand are aligned

exactly and [are] between the 5 and 6 marks.

The hour hand makes jumps of 30 degrees or pi/6 and the minute hand jumps

6 degrees at each interval

the degrees have to be negative to move in a clockwise direction.

conversion from Cartesian to plane polar

[URL]http://upload.wikimedia.org/math/1/e/4/1e45270de98ece45a86492fb57d37263.png[/URL]

I got the jump period and decide to arbitrarily make the scaler for minute 2 and the scaler for hours 1 I just dont understand how to make it move through the degrees in a time varying fashion.

all help greatly appreciated - I just need a clue.

## Homework Statement

Work this problem in both Cartesian (rectangular) coordinates and plane polar coordinates:

Consider an analog watch that keeps perfect time and assume the origin to be at the center of the dial, the x axis passing through the 12 mark, and the y axis passing through the 3 mark.

(a) Write the expression for the time-varying unit vector directed along the hour hand of the watch.

(b) Write the expression for the time-varying unit vector directed along the minute hand of the watch.

(c) Obtain the speciﬁc expression for these unit vectors when the hour hand and the minute hand are aligned

exactly and [are] between the 5 and 6 marks.

## Homework Equations

The hour hand makes jumps of 30 degrees or pi/6 and the minute hand jumps

6 degrees at each interval

the degrees have to be negative to move in a clockwise direction.

conversion from Cartesian to plane polar

[URL]http://upload.wikimedia.org/math/1/e/4/1e45270de98ece45a86492fb57d37263.png[/URL]

## The Attempt at a Solution

I got the jump period and decide to arbitrarily make the scaler for minute 2 and the scaler for hours 1 I just dont understand how to make it move through the degrees in a time varying fashion.

all help greatly appreciated - I just need a clue.

Last edited by a moderator: