Which statement about the greenhouse effect is not true? .

a.) the greenhouse effect keeps earth from becoming too hot during the day.
b.) the greenhouse effect causes the change in seasons.
c.) the greenhouse effect keeps earth from becoming too cold during the night.
d.) the greenhouse effect makes it possible for organisms to live on earth.
e.) the greenhouse effect can be influenced by human activity.

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.