We know that **Rate change of speed, dv/dt= tangential acceleration =tangential force/mass**

When θ=30^{∘}, tangential force is mgsinθ

Therefore F=mgsin30

ma=mgsin30

a=mgsin30/m

=10sin30

=10×1/2

**=5m/s**^{2}

**So, The rate of change of speed of the bob at theta = 30 degree is 5m/s**^{2}