Potential vs. Kinetic Energy Friday, February 6th, 2015

Do Now Enter silently and complete quiz # 14, last word is tungsten when you are finished copy down vocabulary You can use a calculator for the worksheet gravitational PE PE=mgh (units=Joules J) g=gravity 9.8m/s KE=1/2mv2 (units=Joules J) stored energy in a system Energy of an object in motion at that time m=mass (kg) v=speed (m/s) (velocity) m=mass (kg) h=height (m) Kinetic Energy Potential Energy An apple on a tree Gasoline in a car ball=0.5 kg A falling apple A moving car mass=80 kg speed=8 m/s PE= 1 meter KE=

Objectives SWBAT identify a scenario that demonstrates the law of conservation of energy by calculating the potential and kinetic energy. Essential Questions What is the relationship between potential and kinetic energy? How is this related to the law of conservation of energy?

Demonstrating the law of conservation of energy I have a marble with a mass of 10.2 grams We need to convert that to __________ I have a 1 meter stick We convert that to _____________ Speed of the marble when it hits the table is √(19.6m/s) What is the potential energy? What is the kinetic energy?

Law of conservation of energy (we are in a vacuum to ignore air resistance) Potential Energy of a 0.1 kg marble 1 m off of the ground PE=mgh PE=(0.0102kg)(9.8m/s2)(1m) PE=0.09996 J Kinetic Energy when it hits the ground v2=2(h)(9.8m2/s2) v2=19.6(1)m2/s2 KE=1/2mv2 KE=[(0.0102kg)√(19.6m/s)2]/2 KE=0.09996 J Joules=(kg)(m2/s2) Some semi-complicated math to find the speed of the marble when it hits the ground More explanation on how we calculate speed at the ground

Answer the Essential Questions What is the relationship between potential and kinetic energy? How is this related to the law of conservation of energy? Answer in ONE complete sentence for EACH question If an object is held at a specific height, the potential energy will be the same as the kinetic energy when the object hits the ground. This means that all of the energy transfers from potential energy to kinetic energy and no energy is created or destroyed.

Exit Ticket A 20 kg rock is dropped off of the top of the AT&T building (188 m). The velocity when it hits the ground is √(3684.8) m/s2 ~ 60.70255 m/s2). What is the potential energy of the rock at the top of the building? PE=mgh What is the kinetic energy of the rock at the ground? KE=(1/2)mv2 Are they the same? Different? Why?