Recall that given the velocity and wavelength, frequency can be computed as

Substituting the given values, we have
Answer: 477 Hz
Answer:
The force that you must exert on the balloon is 1.96 N
Explanation:
Given;
height of water, h = 4.00 cm = 4 x 10⁻² m
effective area, A = 50.0 cm² = 50 x 10⁻⁴ m²
density of water, ρ = 1 x 10³ kg/m³
Gauge pressure of the balloon is calculated as;
P = ρgh
where;
ρ is density of water
g is acceleration due to gravity
h is height of water
P = 1 x 10³ x 9.8 x 4 x 10⁻²
P = 392 N/m²
The force exerted on the balloon is calculated as;
F = PA
where;
P is pressure of the balloon
A is the effective area
F = 392 x 50 x 10⁻⁴
F = 1.96 N
Therefore, the force that you must exert on the balloon is 1.96 N
You need the kinematic equation for distance as a function of acceleration:
![d = [v(initial) *t] + 0.5a*t^{2}](https://tex.z-dn.net/?f=d%20%3D%20%5Bv%28initial%29%20%2At%5D%20%2B%200.5a%2At%5E%7B2%7D)
where a = gravitational acceleration 9.8m/s^{2}
v(initial) = starting velocity
t = time of fall
if the stone started at rest then v(initial) = 0 making the equation simply

Let me know if you still need further help :)