(2) The second hand moves 360/60=6 degrees per second (just 12×5= 60 steps per second).
(3) After a, 10 seconds, it is found that the second hand oc deviates from 12 point and goes 6× 10=60 degrees.
The minute hand needs 1 hour, that is, 3600 seconds, so the second needs 10 second, and the minute hand needs 10/3600×360= 1 degree.
Therefore, after 10 second, the included angle between the second hand oc and the minute hand oa ∠aoc is 60- 1=59 degrees.
(4) When the clockwise rotation is 1 2× 3600 = 43,200 seconds, then the second hand goes1second and the clockwise hand goes1/43,200× 360 =120 degrees.
Suppose that after x seconds, oc divides ∠aob equally for the first time.
At this time, the angle between the hour hand ob and 12 is 120+x/ 120 degrees.
The included angle between the second hand oc and 12 is 6x degrees.
The angle between the minute hand oa and the 12 direction is x/ 10 degree (second hand moves 1 step, minute hand moves1/3600× 360 =110 degree).
Yes120+x/120-6x = 6x-x/10.
The solution is x≈ 10.09 second.
A: (1); At 4 o'clock sharp, the angle between the hour hand and the minute hand is __ 120__ degrees.
(2); The second hand turns 6 degrees per second.
(3); From 4 o'clock sharp, the minute hand oa is at 12 o'clock and the hour hand ob is at 4 o'clock. If the second hand oc starts to rotate from 12, {A }；; 10 seconds later, the included angle between the second hand oc and the minute hand oa ∠aoc is 59 degrees {B} 10.09 seconds later, oc divides ∠aob equally for the first time (accurate to 0.0 1 second).
I hope it helps you.