Numerical Calculations with Units

The Wolfram Language's unit system utilizes various numerical methods, facilitating calculations using Quantity expressions within the Wolfram Language's numerical functions.
N[quantity]
numerical approximation of the specified quantity
FindRoot[lhsrhs,{x,x0}]
search for a numerical solution to an equation, starting with
FindMaximum[f,{x,x0}]
search for a maximum of f, starting with
Numerical functions that operate on Quantity expressions.
N[quantity] gives you a numerical approximation of quantity:
For numerical functions like FindRoot and FindMaximum, if a variable is specified within a Quantity expression, then that variable is assumed to be a dimensionless value (representing the magnitude of its Quantity). If no unit is specifically associated with a variable, these functions will attempt to automatically determine the units associated with the variable, based on the expression and any specified start values.
Specifying x within a Quantity indicates that x is a dimensionless value:
Find the time it takes for a falling body to hit the ground:
Find a local maximum, starting the search at x=2:
Find the peak height of a bullet fired from a rifle vertically, without dampening:
Find how long it takes the bullet to return to Earth:
Find the maximum height of a body shot vertically upward, with dampening: