An inventive child named nick wants to reach an apple in a tree without climbing the tree. sitting in a chair connected to a rope that passes over a frictionless pulley (fig. p5.81), nick pulls on the loose end of the rope with such a force that the spring scale reads 250 n. nick's true weight is 320 n, and the chair weighs 160 n. nick’s feet are not touching the ground. (a) draw a pair of diagrams showing the forces for nick and the chair considered as separate systems and another diagram for nick and the chair considered as one system. (b) show that the acceleration of the system is upward and find its magnitude. (c) find the force nick exerts on the chair.

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.

Why is the energy that results from a roller coaster's position at the top of a hill referred to as potential energy?

Imagine that you have two balloons (or, better yet, actually inflate two balloons, if possible). create static electricity around one of the balloons by rubbing it against your hair or your sweater and then bring that balloon close to the other balloon, which has not been charged. try this with at least one other object—and for variety in the discussion, avoid using an object already described by your classmates. then, for your initial post to the discussion, answer the following questions: what happened with the two balloons?