The period of the pendulum is the reciprocal of the frequency:

The period of the pendulum is given by

where L is the length of the pendulum, and g the acceleration of gravity. By re-arranging the formula and using the value of T we found before, we can calculate the length of the pendulum L:
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Answer:
(A). The speed of the ions is 
(B). The radius of curvature of a singly charged lithium ion is 
Explanation:
Given that,
Electric field = 60000 N/C
Magnetic field = 0.0500 T
(A). We need to calculate the velocity
For no deflection





(B). We need to calculate the radius
Using magnetic force balance by centripetal force


Put the value into the formula


Hence, (A). The speed of the ions is 
(B). The radius of curvature of a singly charged lithium ion is 
Answer: 0.5 seconds
Explanation:
Given that:
Frequency of the George Washington Bridge F = 2.05 Hz
Period T = ?
Recall that frequency is the number of cycles a wave can complete in one second. Hence, frequency is the inverse of period.
i.e F = 1/T
2.05Hz = 1/T
T = 1/2.05Hz
T = 0.488 seconds (Rounded to the nearest tenth as 0.5seconds)
Thus, the period of the George Washington Bridge is 0.5 seconds