Elastic PE, Power, Test ReviewMonday, 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 ExampleA 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 1A 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 2A 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 4th floor in 9.35 seconds. The motor produces 77077 joules of work. Calculate the power rating of the motor.

Review