Potential and Kinetic Energy What is Energy Energy

Potential and Kinetic Energy

What is Energy ¬Energy – is the ability to do WORK!!! ¬Two types of energy – Potential Energy – Kinetic Energy

Potential and Kinetic Energy

¬Animation ¬http: //www. teachersdomain. org/resource/h ew 06. sci. phys. maf. rollercoaster/

Potential Energy 1. Energy at rest 2. Stored Energy 3. Higher the object - greater the potential energy

Potential Energy ¬Which boulder has the least amount of potential energy and Why?

Types of Potential Energy ¬Elastic potential ¬Gravitational potential energy (GPE) – Energy stored – The amount of by things that GPE an object stretch or compress has depends on its mass, the acceleration due to gravity, and its height above ground.

Elastic Potential Energy ¬Explain how this rubber band has elastic potential energy!

Potential Energy ¬When is the spring having potential energy?

Brain Pop Movie: Potential Energy ¬http: //glencoe. mcgrawhill. com/sites/0078802482/student_view 0/ brainpop_movies. html

Calculating potential energy PEg = m*g*h or PEg =Fw*h Units PEg = gravitational potential energy m = mass g = acceleration due to gravity h = height J or Nm kg m/sec 2 m Fw=Force of Weight N NOTE: Units for kinetic and potential energy are J (joules). 1 joule = 1 kg × m 2/sec 2 = 1 Nm

Potential Energy Problems 1. A weight lifter lifts a 120 kg mass from the floor to a position above his head, 2. 5 meters above the floor. What is the potential energy expressed by the weight? PE= m g h PE = (120)(9. 8)(2. 5) PE= 2940 J The potential energy of the weight is 2940 J.

2. What is the potential energy of a 90 N boat before it falls from the top of a 30 m waterfall? PE = ? Fw = 90 N h = 30 m PE = Fw*h = (90 N) (30 m) PE = 2700 N • m = 2700 J

If the acceleration on a new planet is 5. 2 m/s 2 and a meteor is sitting on a hilltop at 100 m with 650 J of PE, then what is the mass of the meteor?

Kinetic Energy 1. Energy of motion 2. The amount of kinetic energy an object has depends on its mass and its velocity

Calculating Kinetic Energy KE = ½ mv 2 KE = kinetic energy m = mass v = velocity Units J or Nm kg m/sec

Example: What is the kinetic energy of a 120 kg obje moving at 30 m/sec? KE = ½ mv 2 m = 120 kg v = 30 m/sec KE=? KE = ½ (120 kg)(30 m/sec)2 KE = (60 kg)(900 m 2/sec 2) = 54000 kg m 2/sec 2 = 54000 J

Quick Writes: Kinetic Energy ¬Which one has the highest KE? ¬Which one has the least KE? 80 km/h 50 km/h 80 km/h

FLASH CARD

Brain Pop Movie: Kinetic Energy ¬http: //glencoe. mcgrawhill. com/sites/0078802482/student_view 0/ brainpop_movies. html

Potential and Kinetic Energy Practice Problems 1. A 100 kg rock sets at the top of a 50 m cliff. What is the rocks potential energy?

2. A 70 kg rock is falling at 30 m/sec. What is its kinetic energy?

3. A 315 kg object sets at the top of a 50 m building. What is its potential energy?

4. A car has 3600 J of kinetic energy and is going 3 m/sec. What is its mass?