Monday

October 20, 2014

October 20, 2014

Posted by **Anonymous** on Sunday, December 9, 2007 at 3:33pm.

- physics -
**drwls**, Sunday, December 9, 2007 at 4:11pmAssuming the hands are rodlike (which is not true), the torque exerted by a hand is half the length, times the mass, times g, times the sine of the angle that the hand makes with vertical. The direction of the torque must also be considered. It is positive (clockwise) from the 12 to the 6 positions, then the negative.

(a) At 3 PM, only the hour hand exerts a torque because the minute hand is straight up. That torque is

(60 kg)*1.35 m*9.8 m/s^2*1.00 = 794 M*m

(b) This is a trickier one. You have to consider both hands, and the hour hand is between numbers.

(c) Both hands are on a vertical axis of symmetry. Their weight acts along a line that passes through the axis of rotation. There is therefore no torque.

**Answer this Question**

**Related Questions**

physics - A particular tower clock similar to Big Ben has an hour hand 2.70 m ...

physics - At 15 minutes past the hour, a 50 g mouse runs up a grandfather clock ...

physics - At 15 minutes past the hour, a 50 g mouse runs up a grandfather clock ...

physics - When it is 10:00, the hour hand on an analog clock is 300 degrees ...

Physics - A tower clock has an hour hand 2.70 m long with a mass of 60.o kg, and...

Math - The tip of the minute hand of Boston's Custom House Tower clock travels ...

physics - A big clock has a minute hand 3 ft long and a second hand 4 ft long. ...

Physics - A big clock has a minute hand 3 ft long and a second hand 4 ft long. ...

PHYSICS - A big clock has a minute hand 3 ft long and a second hand 4 ft long. ...

trigonometry - a clock has a dial face of 12 inches radius the minute hand is 9 ...