The helicopter in the drawing is moving horizontally to the right at a constant velocity. the weight of the helicopter is w=42500 n. the lift force l generated by the rotating blade makes an angle of 21.0° with respect to the vertical. (a) what is the magnitude of the lift force? (b) determine the magnitude of the air resistance r that opposes the motion.

Aspring has a relaxed length of 33 cm (0.33 m) and its spring stiffness is 6 n/m. you glue a 76 gram block (0.076 kg) to the top of the spring, and push the block down, compressing the spring so its total length is 15 cm. you make sure the block is at rest, then at time t=0 you quickly move your hand away. the block begins to move upward, because the upward force on the block by the spring is greater than the downward force on the block by the earth. calculate y vs. time for the block during a 0.09-second interval after you release the block, by applying the momentum principle in three steps each of 0.03-second duration.