$| F |=\left|a \sin k_1 x\right|=\left|b \sin k_2 T \right|$
Since arguments can't have units, thus, $\left|k_1 x\right|=\left|k_2 T\right|=M^0 L^0 T^0$
Thus, $\left| k _1\right|= L ^{-1}$ and $\left| k _2\right|= T ^{-1}$
Thus units will be $k _1-$ metre $^{-1}$ and $k _2- s ^{-1}$.