Quick Question: What is elastic potential energy and where are some places you would find it? Why were traditional bamboo and metal poles used in vaulting replaced with fiberglass poles? Describe the changes in energy that occur when Brian vaults over a high bar. Consider the work done on a bow before an arrow is launched. Is the work done positive or negative work? Why?

Assignments due from absent last week: Energy Lab with the tracks What Much Energy would I use? (Link from F&H page) It’s All Uphill Worksheet ( Link form F&H Page) Page 287 Problems 1-3 Page 291 Problems 4-8 Quiz on concepts Tuesday 5/2

Today’s Objective: Share projects for this marking period Come up with requirements for third project What are the rules we must follow? How will the project be graded? How will the physics we are learning be used? How will the teams be determined? What kind of materials are needed? Who will be on each of the teams? Who will be responsible for clean up?

Suppose a 5-kg mass, initially at rest, is accelerated to a final velocity of 8 m/sec in 4 seconds across a frictionless surface. What acceleration does it experience? How large a force was acting on it to accomplish this task? 3. Suppose the mass is now pulled across a second surface which is no longer smooth. On this rough surface, the object encounters a constant frictional “retarding force” of 7 Newtons as it moves forward. How large would the new pulling force have to be to achieve the same acceleration?

How much work is done on 5 kg mass when the object is pulled 16 meters across the original frictionless surface by a 10 N force? How much work is done on our 5 kg mass by the 7N frictional force when the object was pulled 16 meters across the rough surface?  How much kinetic energy did the 5-kg mass gain as it was accelerated from 0 to 8 m/sec in 4 seconds?

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