Lecture-Example (posted before lecture) 9/30 (Friday) Question: What is the period of the moon orbiting around the Earth? Orbital radius: 3.48x108 m. Mass of Earth: 5.98x1024 kg. Example: Geostationary satellite. Communication {like TV,..) satellites appear to "hover\" over one point on the earth's equator. A satellite that appears to remain stationary as the earth rotates is said to be in a geostationary orbit. What is the radius of the orbit of such a satellite? Example A 2.0 kg is lying on a 0.75 m high table. You pick it up and place it on a bookshelf 2.3 m above the floor. During the process, (a) How much work does your hand do on the book? (b) how much work does gravity do on the book? Example John pulls a crate having mass 20 kg along a rough horizontal floor with a force of 80 N that is 30 above the horizontal. If the coefficient of friction is 0.25, (a) what is the acceleration and (b) what is the speed after the crate slides 15 m if it starts from rest? 9 Draw a free-body force diagram. 9 Find gravitational force, normal force, and friction. 9 Find the acceleration How much work does John do on the crate as it slides 15 m? How much work does normal force do on the crate as it slides 15 m? How much work does gravity do on the crate as it slides 15 m? How much work does friction do on the crate as it slides 15 m? What is the total work done on the crate as it slides 15 m