# Learning Goal: Students will be able to… - explain how work and energy are related - perform calculations related to kinetic energy and work.

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Learning Goal: Students will be able to… - explain how work and energy are related - perform calculations related to kinetic energy and work

Energy: Energy: The ability to cause change in self or surroundings. Work: A transfer of energy by physical means. Discuss: What are some forms of energy with which youre already familiar? (And how do those forms match the definition of energy?)

Kinetic Energy: Energy possessed by an object due to its motion. KE = ½mv 2 Unit: kg(m/s) 2 = Joules

Example Problem: If a 10kg ball possesses 2000J of kinetic energy, how fast must it be moving? Answer: 20m/s

The Work-KE Theorem: Discuss: If an object is at rest, then 40J of net work are done on the object, whats the object doing now? So… If a net amount of work is done on an object, energy is transferred to (or from) the object, and the objects kinetic energy will change.

The Work-KE Theorem: W net = KE …or… Fdcos = ½mv f 2 - ½mv i 2

Example Problem: A 50N net force acts on a 12kg object, increasing its speed from rest. If that force acts through a distance of 5m, what is the final speed of the object? Answer: 6.45m/s

Todays HW Answers: 44. The truck required more work. 49.The more massive skater requires a larger stopping distance. 54.125,000J 60.66m 70.a. 86,490J b. 3931N Pg. 306-308 #44, 49, 54, 60, 70

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