The sound wave produced by striking the middle C key on a piano has a frequency

35.71 N

Explanation:

The elevator starts from the rest means its initial velocity is zero.

Given that, the height achieved by the elevator in 1.4 s will be,

Given that the mass of the bundle which is hold by passenger is,

Now according to second equation of motion.

Here, S is the height, u is the initial velocity, t is the time taken, and a is the acceleration.

Now initial velocity is zero therefore,

According to the free body diagram tension and acceleration in upward direction and weight is in downward direction.

So,

Put the value of a from the above

Put all the variables.

This the required tension.