Announcements M: Power T: Internal Energy + Student Questions W: Lab R: Quiz/Test? F: Momentum and Impulse (Momentum Sub-Unit)

Unit 3: Energy and Momentum Energy Objectives: 1. Define work and calculate the work done by a force. 2. Calculate the kinetic energy of a moving object. 3. Determine the gravitational potential energy of a system. 4. Calculate the power of a system. 5. Apply conservation of energy to analyze energy transitions and transformations in a system. 6. Analyze the relationship between work done on or by a system, and the energy gained or lost by that system. 7. Use Hooke's Law to determine the elastic force on an object. Calculate a system's elastic potential energy.

Power is defined as the rate at which work is done It is often important to know not only if there is enough energy available to perform a task but also how much time will be required. Power is defined as the rate at which work is done W P = t Note: Two people can do the same amount of work, but the one doing it faster (in less time) will have the greater power output.

Power Units Since work is measured in Joules (J) and time is measured in seconds (s) the unit of power is Joules per second (J/s). However, in honor of James Watt, who made critical contributions in developing efficient steam engines, the unit of power is also know as a Watt (W). W P = t

P= Fdparallel P= dparallel P = (F) P = (F) v Power W t Since W = Fd parallel P= t dparallel P = (F) t Since v = d/t P = (F) v So power can be defined as the product of the force applied and the velocity of the object parallel to that force.

Work time (Finish worksheet)