Answer:
4.29 millimeters
Explanation:
Bats emit ultrasound waves: in air, ultrasound waves travel at a speed of

The frequency of the waves emitted by this bat is:

Therefore we can find the wavelength of the wave emitted by the bat by using the relationship between speed, frequency and wavelength:

Hi there!
For this part, we can disregard the horizontal velocity because horizontal and vertical motion are INDEPENDENT.
We can used the simplified equation to solve for time:

Where:
h = height
g = acceleration due to gravity (assume g = 10 m/s²)
Plug in given values:

t ≈3.162 sec
Explanation:
PE = KE
mgh = ½ mv²
v = √(2gh)
v = √(2 × 9.8 m/s² × 0.75 m)
v = 3.83 m/s