In 1644, Marin Mersenne calculated that a pendulum with a length of 39.1 inches ( 0.994 m ) would have a period at one standard gravity of precisely two seconds, one second for a swing forward and one second for the return swing, enabling such a pendulum to tick in precise seconds.
42.
To convert the Vickers hardness number to SI units the hardness number in kilograms-force per square millimeter ( kgf / mm?) has to be multiplied with the standard gravity ( 9.806 65 ) to get the hardness in MPa ( N / mm?) and furthermore divided by 1000 to get the hardness in GPa.
43.
:If it's'free falling'and we are neglecting air resistance, the only force is gravity-so the acceleration must be'g'( the accelleration due to Standard gravity ) which is about 9.8ms-2 ( although it varies a bit depending on where you are on the earth ).
44.
(The equation can also be written using the specific impulse instead of the effective exhaust velocity by applying the formula v _ \ text { e } = I _ \ text { sp } \ cdot g _ 0 where I _ \ text { sp } is the specific impulse expressed as a time period and g _ 0 is standard gravity H " 9.8 m / s 2 .)
45.
In the small-angle approximation, the potential energy of a single pendulum system is \ tfrac12 \ tfrac { mg } { L } x ^ 2, where " g " is the standard gravity, " L " is the length of the pendulum, " m " is the mass of the pendulum, and " x " is the horizontal displacement of the pendulum.
