C. 4 N is the answer if not then i be dumb!!!
Answer:
Options d and e
Explanation:
The pendulum which will be set in motion are those which their natural frequency is equal to the frequency of oscillation of the beam.
We can get the length of the pendulums likely to oscillate with the formula;

where g=9.8m/s
ω= 2rad/s to 4rad/sec
when ω= 2rad/sec

L = 2.45m
when ω= 4rad/sec

L = 9.8/16
L=0.6125m
L is between 0.6125m and 2.45m.
This means only pendulum lengths in this range will oscillate.Therefore pendulums with length 0.8m and 1.2m will be strongly set in motion.
Have a great day ahead
Each
ion contains three extra protons. Hence, the extra charge on each
=
C
Total charge = 0.035 pC
Total charge (Q) =
C
Let the number of
ions be n.
According to question:



n = 72917
Hence, the total number of ions needed to be transferred is 72917