Bola A dan B masing-masing bermassa 10 kg dan 30 kg, akan bertumbukan seperti tertera pada gambar di atas. Jika kedua benda menyati setelah tumbukan, maka kecepatan kedua benda tersebut setelah tumbukan adalah...

The answer is observations and interpreting.

This is the most closely resembles the model. 

Many archeologists and anthropologists disagree with dr. thorne's view.  thorne strongly believes that what many calls "homo erectus"  was in fact  homo sapiens,  and that they migrated out of africa almost 2 million years ago and dispersed throughout europe and asia. that's way different  from what scientists have always believed about the evolution of the species.