The texture of obsidian is best described as glassy. why does obsidian contain few or no mineral grains? by the way i put it under physics because that's what it's labeled as on my side.

A6.0-kilogram cart initially traveling at 4.0 meters per second east accelerates uniformly at 0.50 meter per second squared east for 3.0 seconds. what is the speed of the cart at the end of this 3.0 second interval? (1) 1.5 m/s (3) 3.0 m/s (2) 5.5 m/s (4) 7.0 m/s