# Chapter 12: Energy & Work Unit Integrated Science I.

## Presentation on theme: "Chapter 12: Energy & Work Unit Integrated Science I."— Presentation transcript:

Chapter 12: Energy & Work Unit Integrated Science I

 Kinetic energy is the energy of motion  Measured in Joules (J)  Depends on two variables ◦ The amount of mass of the object ◦ The velocity of the object Kinetic Energy

K.E. = ½ m x v 2 K.E. = Kinetic Energy (J) m = mass (kg) v = velocity (m/s) How to Calculate K.E.:

 Determine the kinetic energy of a 625-kg roller coaster car that is moving with a speed of 18.3 m/s. ◦ Equation: KE = ½ m x v 2 ◦ Substitute: KE = ½ (625 kg) x (18.3 m/s) 2 ◦ Simplify: KE = (312 kg) x (334.9 m/s) ◦ Answer: KE = 104,468.7 J Kinetic Energy Practice Problem

 Gravitational potential energy is energy not moving yet  Stored in an object as the result of it being above the ground  GPE is measured in Joules (J)  Objects have more GPE when… ◦They have more mass ◦They are higher off the ground Gravitational Potential Energy (GPE)

G.P.E. = m x g x h GPE = gravitational potential energy (J) m = mass (kg) g = gravity (10 m/s 2 ) h = height of object (m) How to Calculate G.P.E.:

 A plate of spaghetti has potential energy because it is hanging off the counter. The plate of spaghetti has a mass of 1.3 kg and is sitting on a 1.2 meter high counter. How much potential energy does the spaghetti have? ◦ Equation ◦ Equation: PE = M x H x 9.8 m/s 2 ◦ Substitution: PE = (1.3 kg) x (1.2 m) x (10 m/s 2 ) ◦ Answer ◦ Answer: GPE = 15.6 J Potential Energy Practice Problem!!

 Energy cannot be created or destroyed  This means energy is never lost – it is only transformed.  Most common type of energy transformation: ◦ Friction: if friction was not present, the total amount of energy in a system would always be the same!!!  Instead – kinetic energy is transformed to thermal energy Law of Conservation of Energy

 Work requires, 1) movement and 2) movement in same direction as the force  Press your hand against the desk as hard as you can. Are you doing any work? ◦ No! ☹ Why not?  Work is the transfer of energy that occurs when a force makes an object move.  You did not make the object move, therefore you did not do any work. Work is the Transfer of Energy!!

 Force and movement MUST BE IN THE SAME DIRECTION!! W = f x d w = work (J) f = force (N) d = distance (m) How to Calculate Work:

Work Practice Problem!!!  You move a 100-kg roller coaster car 30 meters because it broke down. This requires a force of 70 N. How much work, in joules, was done while moving the roller coaster car? ◦ Equation: W = f x d ◦ Substitution: W = (70N) x (30m) ◦ Answer: W = 2,100 J