Let's again see why this is true. {{CMD_83}} If an apple has a mass of {{MATH_84}}, how much work is required to lift this apple {{MATH_85}} meter? Assume that the acceleration due to gravity is {{MATH_86}}. {{CMD_87}} Well, work is computed by {{MATH_88}} Since force is mass times acceleration, {{ENV_89}} So, our integral becomes {{ENV_90}} Ah! So when lifting an apple {{MATH_91}} meter, requires {{MATH_92}} joules of work. The sign is negative since we are lifting {{CMD_93}}against{{CMD_94}} the gravitational force. {{CMD_95}} {{CMD_96}}