# Elastic PE, Power, Test Review Monday, September 15, 2014.

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Elastic PE, Power, Test Review Monday, September 15, 2014

Tuesday, 9/16 Unit 2: Work, Power, and Energy  Pick up a calculator or take out your calculator  Pick up warm up from the Physics bin and complete (3 minutes)  Upcoming dates  ‘B’ day Unit 2 test – Thursday, 9/18  Unit 2 missing work due – Thursday, 9/18 (by your testing period)  Review due for extra points (6 points) – Thursday, 9/18 (when the late bell rings)  Last day to turn in 1SW extra credit – Monday, 9/22

Warm-up 1.Label the KE and draw the letters to scale. 2. Describe the transfer of energy of the boy on the swing

Elastic Potential Energy

Elastic Potential Energy Example A plastic bullet with a mass of.45 kg is put into a toy gun. The spring in the gun has a spring constant of 200 N/m. The spring is compressed.20 meters before the bullet is released. What is the potential energy of the bullet before the trigger is pulled?

Practice Problem 1 A plastic bullet with a mass of.20 kg is put into a toy gun. The spring in the gun has a spring constant of 100 N/m. The spring is compressed 4.0 x 10 -3 meters before the bullet is released. What is the potential energy of the bullet before the trigger is pulled?

Practice problem 2 A plastic bullet with a mass of.35 kg is put into a toy gun. The spring in the gun has a spring constant of 300 N/m. The spring is compressed 6.0 x 10 -3 meters before the bullet is released. What is the potential energy of the bullet before the trigger is pulled?

Power CNs

Power practice problem 1 Bart runs up a 2.91 meter high flight of stairs in 2.15 seconds. Bart produces 1879.3 J of work. Calculate Bart’s power.

Power practice problem 2 An elevator motor lifts 715 kg of mass to the height of the fourth floor of an office building. The elevator reaches the 4 th floor in 9.35 seconds. The motor produces 77077 joules of work. Calculate the power rating of the motor.

Review