If the height doubled, the car would have gravitational potential energy twice the original . If both cars are lifted to the same elevation, the car twice as massive has twice as much gravitational potential energy. Therefore, the second car has the larger kinetic energy. If the speed becomes 4 times, the kinetic energy becomes 16 times as much. Part of the chemical energy in a green leaf comes from the sun.
Green plants can produce hydrocarbon compounds such as sugar by combining water and carbon dioxide.
This process is photosynthesis and is energized by sunlight. The person will then gain weight. The person will then lose weight. It will be very hard for an undernourished person to perform extra work without extra food. Choose the lowest point as the reference point for potential energy.