In the figure, the lever arm, l, is distance r from the hinge to the point at which you exert your force. The torque is the product of the magnitude of the perpendicular force multiplied by the lever arm.
Children normally need a certain number of calories each day (energy allowance) that their bodies use as energy for normal daily activities (walking, breathing, etc.). This ranges for boys from 2000 calories for a 7-10 year old, 2500 calories for an 11-14 year old, and 3000 calories for a 15-18 year old. For girls the ranges are from 2000 calories for a 7-10 year old, to 2200 calories for an 11-18 year old. These are only estimates and some children need more (fast metabolism) or less (slow metabolism) of an energy allowance for daily activities.
Men aged 19-51 years of age require even more, anywhere between 2,200-2,400 calories per day. People that lead more active lifestyles or those who want to gain weight require more calories. For children aged between 2 and 18 years, calorie intake ranges from anywhere between 1000-2200 per day. A full list of daily calorie needs can be found at ChooseMyPlate.gov.