Designing warning and evacuation systems could be a step in a plan designed to mitigate the negative impacts of a natural hazard.
The hang time of the ball is 4.08 s
Explanation:
The ball is in free fall motion: this means that it is acted upon gravity only, so its acceleration is the acceleration of gravity,

downward (the negative sign refers to the downward direction).
Since this is a uniformly accelerated motion, we can solve the problem by using the following suvat equation:

where
v is the final velocity
u is the initial velocity
a is the acceleration
t is the time
First we calculate the time it takes for the ball to reach the maximum height, where the velocity is zero:
v = 0
Substituting:
u = +20 m/s

we find t

The motion of the ball is symmetrical, so the total time of flight is just twice the time needed to reach the maximum height, therefore:

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Answer:
Seriously I have no idea. I need help with my homework.
Explanation:
I really need help with my homework. Sorry
The major reason why a wet saw that is used in cutting optical crystals is constantly lubricated with oil is largely due to friction, lubrication decreases friction and minimises the increase of internal energy.
Friction is basically the coming together of two parts that rubs against each other, it causes heat and lead to deterioration of surfaces, it can also lead to wear and tear.
Although, despite it down side, friction is desire-able in most applications
e.g the brake system of vehicles, and if not for friction, we humans cannot walk without falling
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