ASTR 101 1st Edition Lecture 9 Outline of Last Lecture I Clicker questions II Newton s law of motion Outline of Current Lecture I Clicker questions II Conservation laws in astronomy III Basic types of energy Current Lecture I Clicker questions a Which of the following was Newton s insight about gravity it is responsible for the motion of the Moon around Earth Gravity is the change in an object s acceleration so the force itself does not necessarily produce a change since that is the actual definition of gravity b Newton s second law of motion states the acceleration of an object is equal to the force acting on it divided by its mass c All of Newton s laws of motion express the concept that a force and only a force always changes the momentum of an object II Conservation laws in astronomy a What is required to change an object s angular momentum a transfer of angular momentum to another object b The energy of earth s rotation is an example of kinetic energy c Conservative momentum d Angular momentum is conserved as Earth orbits the Sun i When the planet is closer to the sun it will move faster And the speed will also be faster if the radium is smaller ii Momentum L mV iii Can t change unless an external twist torque acts upon it When the orbit changes then angular momentum will change Angular momentum also exists for objects moving in straight lines III Basic types of energy energy can change its type but cannot be destroyed a Kinetic energy K mv2 b Radiative energy light electromagnetic waves These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute c Stored potential energy EX we have the potential to fall after standing but currently we are not falling EX chemical potential energy we require potential energy from the food we eat by storing that energy and using it later d Thermal energy the collective kinetic energy of many particles It depends on temperature and density e Gravitational potential energy depends on mass strength of gravity and distance the object could fall