A driver starts his car resting on top of a semicircular hill. The road leading to the foothills is frictionless and curved. Derive an equation to calculate the car's speed at an angle θ as depicted in the figure below.

• A. √(gh(1 + cosθ))
• B. √(gh(1 - cosθ)
• C. √(2gh(1 + cosθ))
• D. √(2gh(1 - cosθ))

Answer: (D)