Um painel coletor de energia

solar é utilizado para aquecer a água de uma

residência e todo o sistema tem um rendimento de

60 %. Para aumentar a temperatura em 12,0 °C de

uma massa de água de 1.000 kg a energia solar total

coletada no painel deve ser de

Dado: considere o calor específico da água igual a

4,0 J/graus C

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.