Hello candidate,

Erg is a unit of energy which in terms of mass, length and time is represented as MLT^-2, where mass is represented in terms of KG, length is represented in terms of metre, and time is represented in terms of seconds.

So if the system has length as 10 centimetre or 0.1 metres, 20 g is equal to 0.02 kg, and 1 hour equal to 3600 seconds. So, MLT^-2, gives 0.02*0.1/(3600*3600)= 0.0015* 10^-7 Newton.

Hope it Helps!!