The frequency of the second hand on a clock is
a) 1 hz.
b) 60 hz.
c) 1/60 hz.

C) 1/60 Hz

Explanation:

The frequency is equal to the reciprocal of the period:

where T is the period.

The period is the time the object takes to do one complete cycle. For the second hand, the period is

T = 60 s

Since this is the time it takes to complete one cycle. Therefore, its frequency is

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.