The quantities which have the same dimensions as those of solid angle are:

A force defined by $$F=\alpha t^2+\beta t$$ acts on a particle at a given time $$t$$. The factor which is dimensionless, if $$\alpha$$ and $$\beta$$ are constants, is:

The diameter of a spherical bob, when measured with vernier callipers yielded the following values : $$3.33 \mathrm{~cm}, 3.32 \mathrm{~cm}, 3.34 \mathrm{~cm}, 3.33 \mathrm{~cm}$$ and $$3.32 \mathrm{~cm}$$. The mean diameter to appropriate significant figures is :

The mechanical quantity, which has dimensions of reciprocal of mass $$(\mathrm{M}^{-1})$$ is :