Explanation: Newton's first law of motion states that a body at rest remains at rest, or, if in motion, remains in motion at a constant velocity unless acted on by a net external force. This is also known as the law of inertia. Inertia is the tendency of an object to remain at rest or remain in motion.
"Changing water salinity" is the most significant challenge for organisms that live in estuaries.
<u>Answer:</u> Option D
<u>Explanation:</u>
For estuaries, alkalinity levels are usually the maximum at a river's mouth where the ocean water falls for, and the minimum upstream where freshwater falls in. Although salinity vary throughout the tidal cycle. In estuaries, salinity rates usually decrease in spring as snow melt and rain raises the freshwater flow from streams and groundwater.
It influences the chemical environments within the estuary, especially the dissolved oxygen (DO) levels in the water. The level of oxygen that would get dissolved in water or its solubility get declined when the alkalinity rises.
Answers:
a) 
b) 
c) 
Explanation:
<h3>a) Impulse delivered to the ball</h3>
According to the Impulse-Momentum theorem we have the following:
(1)
Where:
is the impulse
is the change in momentum
is the final momentum of the ball with mass
and final velocity (to the right) 
is the initial momentum of the ball with initial velocity (to the left) 
So:
(2)
(3)
(4)
(5)
<h3>b) Time </h3>
This time can be calculated by the following equations, taking into account the ball undergoes a maximum compression of approximately
:
(6)
(7)
Where:
is the acceleration
is the length the ball was compressed
is the time
Finding
from (7):
(8)
(9)
(10)
Substituting (10) in (6):
(11)
Finding
:
(12)
<h3>c) Force applied to the ball by the bat </h3>
According to Newton's second law of motion, the force
is proportional to the variation of momentum
in time
:
(13)
(14)
Finally:

The <span>stream's discharge
The volume of water to pass a given point on a stream bank per unit of time, usually expressed in cubic meters of water per second. </span>
You're supposed to divide the mass by the volume, which is going to equal to 5