Max ang. speed(u) = 18 rad/s
final ang. speed(v) = 0
ang. displacement(s) = 220 rad
ang. acceleration = (v^2 - u^2)/2s = -18^2 / 2*220 = -0.7364 rad/s^2
v = u +at
0 = 18 - 0.7364t
t = 18/0.7364
t = 24.44 seconds
Answer:

Explanation:
The Hi line of the Balmer series is emitted in the transition from n = 3 to n = 2 i.e.
and 
The wavelength of Hi line of the Balmer series is given by :




So, the wavelength for this line is 550 nm. Hence, this is the required solution.
Answer:
When the doctor has the syringe, it is full of air. So, now after the doctor pushes the plunger, hence the air gets released into the medicine container. After this the doctor then takes the plunger and pull it back. Now , the air gets pulled up back into the syringe, but not only does the air come in but also the medicine because of the pressure build up.
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It has 99 electrons because an element has the same number of protons and electrons