I have a question specifically about the unit conversio in this question: In 200

Question

I have a question specifically about the unit conversio in this question:

In 2003, an earthquake in Japan generated waves that traveled outward at 7.0 { m km}/{ m s}. 200 { m km} to the west, seismic instruments recorded a maximum acceleration of 0.25 { m g} along the east-west axis at a frequency of 1.1 { m Hz}. a.) What was the wavelength? b.) What was the maximum horizontal displacement of the ground as the wave passed? I already found the answer to part a.) which is 6400m. I need help with part b. I found another post where the work was shown.

a max= 0.25g x 9.8m/s ^2 = 2.45

a max = (2 x pi x f)^2 x A.

--> A = a max / (2 x pi x f)^2
= 2.45 /(2 x pi x 1.1)^2
= 0.0512 m --> Answer

My question is...why didn't we have to convert grams to kg? This is the correct answer, but something is eluding me in regards to the unit conversion. Any help would be greatly appreciated!

Explanation / Answer

[Spectral acceleration (SA) is a unit measured in g (the acceleration due to Earth's gravity, equivalent to g-force) that describes the maximum acceleration in an earthquake on an object – specifically a damped, harmonic oscillator moving in one physical dimension. This can be measured at (or specified for) different oscillation frequencies and with different degrees of damping.]

g is used not for gram or kg. It is used for acceleration due to gravity.

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