Roshan makes the table below to describe how to draw a ray diagram for a convex lens.
what error did roshan make?
the ray that goes through the center should bend and go through the focal point on the other side.
the ray that starts out parallel with the main axis should bend toward the axis and go through the focal point on the other side.
the ray that goes parallel to the main axis after passing through the lens should also be parallel from the object to the lens.
the rays in the table describe how rays are drawn for a concave lens rather than for a convex lens.

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.