When the tucurui dam was constructed in northern brazil, the lake that was created covered a large forest of valuable hardwood trees. it was found that even after 15 years underwater the trees were perfectly preserved and underwater logging was started. during the logging process a tree is selected, trimmed, and anchored with ropes to prevent it from shooting to the surface like a missile when cut. assume that a typical large tree can be approximated as a truncated cone with a base diameter of 13 ft, a top diameter of 7.6 ft, and a height of 82 ft. determine the resultant vertical force that the ropes must resist when the completely submerged tree is cut. the specific gravity of the wood is approximately 0.6 .

Askydiver weighing 140 lb (including equipment) falls vertically downward from an altitude of 19,000 ft and opens the parachute after 18 s of free fall. assume that the force of air resistance, which is directed opposite to the velocity, is of magnitude 0.55|v| when the parachute is closed and is of magnitude 14|v| when the parachute is open, where the velocity v is measured in ft/s. assume that acceleration due to gravity has magnitude 32 ft/s/s; remember that weight is the product of mass and gravitational acceleration. (a) find the speed of the skydiver when the parachute opens. (b) find the distance fallen before the parachute opens. (c) what is the limiting velocity vl after the parachute opens? (d) determine how long the sky diver is in the air after the parachute opens. (e) plot the graph of velocity versus time from the beginning of the fall until the skydiver reaches the ground.

An object weigh 40n in air ,weigh 20n when submerged in water,and 30n when submerged in a liquid of unknown liquid density.what is the density of unknown of liquid?

Select all the correct answers. which three statements about electromagnetic radiation are true?