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Science Starter • Take out your yellow sheet and complete next 2 problems • Take the first 5 minutes and try to complete them on your own!! • Place on your desk: Modeling Energy (both HWs), Conservation of Energy Lab AP EXAM SIGN UP DEADLINE FOR SUBMITTING PAPER WORK EXTENDED TO TODAY 4pm Today’s Agenda • Science Starter- Warm Up Review Packet Final • Energy & Work • Energy & Non-conservative Forces Lab • Davidson NEXT • Unit 4 Summary Lesson Essential Question What does it mean for energy to be conserved? • Kinetic Energy is energy of motion Energy & Work K=1/2(m)v2 • Gravitational Potential Energy Basic Energy Model Ug=mgh • Work: transfer of energy by mechanical forces (W=Fdcosθ) • Elastic Potential Energy 2 U =1/2(k)x s • When work is done on a • Thermal Energy (friction) system, the system’s total energy changes by the amount ΔEth = fkΔx of work done • If a system is isolated and friction is present then… ΔE=ΔK+Δug+…=W Kf+(Ug)f+(Us)f+ΔEth = Ki+(Ug)i+(Us)i • If a system is isolated, W=0 Energy & Non-Conservative Forces Lab • Problem: Determine the amount of energy dissipated by friction in a system consisting of a modified Atwood machine (.5 meters) • Materials: Wood block, wood board, frictionless pulley, string, meter stick, mass, mass hanger • What information are you given? • Coefficient of friction: u=0.4 • Mass of block: 0.7 kg • Lab must include: procedures, system, bar charts, mathematical representations, data table and analysis, conclusion, and explanation of any errors Modified Atwood Machine (50 minutes) Davidson NEXT • Take a computer and go to the following website: edge.edx.org • Login using your username you created and a password • You should see a course for Physics 1 • When you open the course go to Rotational Motion • Read Overview & Objectives, continue on through the module in order • Can do alone or in partners! Summary & Homework • Complete the conservation of energy problems • Watch intro to momentum video (Khan Academy) https://www.youtube.com/watch?v=XFhntPxow0U • Complete Lab Report (same rubric as last lab) Checking Our Work • Experimental Values: • What you find in the lab • Should have found velocity, height, distance moved, and masses of moving pieces • Actual Values: • What the numbers should be • Check your work with the following equation Wfriction=ΔE= fkΔx=ukmgΔx=(0.4)(0.7 kg)(9.8m/s2)(0.5m)=1.372 J Calculating Percent Error