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.

You are driving directly behind a pickup truck, going at the same speed as the truck. a crate falls from the bed of the truck to the road. (a) will your car hit the crate before the crate hits the road if you neither brake nor swerve? (b) during the fall, is the horizontal speed of the crate more than, less than, or the same as that of the truck?