we are given
displacement is
[tex]x=asin(2\pi ft)[/tex]
now, we are given
rigonometric function appearing in an equation must be dimensionless
so,
[tex]sin(2\pi ft)[/tex] must be dimensionless
so, unit of x and unit of 'a' must be same
so, unit of 'a' will be unit of displacment
and unit of displacemet is metre(m)
so, unit of 'a' will be metre(m).............Answer