Answer:
1) The greatest height attained by the ball equals 20.387 meters.
2) The time it takes for the ball to reach 15 meters approximately equals 1 second.
Explanation:
The greatest height will be attained when the ball stop's in the air and starts falling back to the earth.
thus using third equation of kinematics we obtain the height attained as

where
'v' is the final speed of the ball
'u' is the initial speed of the ball
'a' is the acceleration that the ball is under which in this case equals 9.81 
's' is the distance it covers
Thus for maximum height applying the values in the equation we get

Using the same equation we can find the speed of the ball when it reaches 15 meters of height as

the time it takes to reduce the velocity to this value can be found by first equation of kinematics as

The amount of water needed is 287 kg
Explanation:
The amount of energy that we need to produce with the power plant is

We also know that the power plant is only 30% efficient, so the energy produced in input must be:

The amount of water that is needed to produce this energy can be found using the equation

where:
m is the amount of water
is the specific heat capacity of water
is the increase in temperature
And solving for m, we find:

Learn more about specific heat capacity:
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Answer:2.517 J/K
Explanation:
Given
Reservoir 1 Temperature 
Reservoir 2 Temperature 
Let Q is the amount of heat Flows i.e. 
thus change in Entropy is given by 



Answer:
self-contained, short-term light-source
Explanation:
Answer:

Explanation:
We must use conservation of linear momentum before and after the collision, 
Before the collision we have:

where these are the masses are initial velocities of both players.
After the collision we have:

since they clong together, acting as one body.
This means we have:

Or:

Which for our values is:
