Answer:
The unit is usually seconds. But it really depends on the situation you are in. If you are talking about uranium-238, then you'll be talking about a half life in the billions of years. However, if you are talking about the half-life of a muon, then it'll be in seconds or microseconds.
Answer:

Explanation:
From the question we are told that:
Mass 
Height 
Speed 
Angle 
Generally the equation for K.E is mathematically given by
Since
The potential energy and kinetic energy is equal to the kinetic energy as it hits the ground.
Therefore



<span>Mechanical waves require a medium
and electromagnetic waves do not.</span>