Explanation:
The equation of motion of an object is given by :

Where
t is the time in seconds
We need to find the time when the object hits the ground. When the object hits the ground, h(t) = 0
So,


On solving above equation using online calculator, t = 8 seconds. So, the object hit the ground after 8 seconds. Hence, this is the required solution.
Answer choice d is correct
Answer:

Explanation:
The frequency of a wave can be found using the following formula.

where <em>f</em> is the frequency, <em>v</em> is the velocity/wave speed, and λ is the wavelength.
The wavelength is 10 meters and the velocity is 200 meters per second.
- 1 m/s can also be written as 1 m*s^-1
Therefore:

Substitute the values into the formula.

Divide and note that the meters (m) will cancel each other out.


- 1 s^-1 is equal to Hertz
- Therefore, our answer of 20 s^-1 is equal to 20 Hz

The frequency of the wave is <u>20 Hertz</u>