What physical force attracts the anti-codon on tRNA to the codon on mRNA during translation?
As with many processes in cellular biology, nothing really moves anywhere, attracted by specific force. What that means, is that any molecule has a chance to interact with any other molecule, say, bind to it. Only force that is acted is electrical force of attraction of negative charges to positive ones.

Due to diffusion and temperature fluctuations, molecules wander around, bumping in each other. Sometimes, two complimentary molecules will bump into each other in a very desirable, energy-efficient orientation. Their atomic-scale interfaces (with tiny charges on it) will find each other as neat as hand finds glove of the right size/orientation neat and comfy. That is the way, for example, tRNA finds slot on ribosome/mRNA complex to plug into. just simple key-and-lock, or hand-and-glove model, that's all there is. And beauty is that you can try computationally calculate probability and energy of different interactions from molecular 3D structures.

Now, there are many tRNAs, but Glycine-tRNA will bind tightest to glycine-codon/ribosome complex. There is a chance that Alanine-tRNA will get in that spot, but that chance is very little compared to chance of proper interaction. Also, because interfaces of Ala-tRNA and Ala-codone don't match exactly, molecular vibration due to heat (temperature) will destroy this complex quickly. This allows specificity.