Which best describes why heat pumps are reversible? They can heat and cool an indoor space.
They involve a metal expanding or contracting against another.
They combust and can also add coolant.
They allow a piston to move up and down.

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?