1. Chapter 15 Sections 1-2

2.  Energy is the ability to do work.  Energy is measured in Joules, just like work.

3.  The energy of motion is called kinetic energy.  To calculate the kinetic energy of an object, multiply half the object’s mass (m) by its speed (v) squared. FORMULA: KE = ½ mv 2  Potential energy is energy that is stored as a result of position or shape.  The potential energy of an object that is stretched or compressed is known as elastic potential energy.

4.  Potential energy that depends on an object’s height is called gravitational potential energy.  Gravitational potential energy is calculated by multiplying the object’s mass (m) by the acceleration due to gravity (g) and its height above the ground (h). FORMULA: GPE = mgh g = 9.8 m/s/s

5.  Find the kinetic energy of a 0.1kg toy truck moving at a speed of 1.1 m/s. KE = ½ mv 2 KE = ½ (0.1kg)(1.1m/s) 2 KE = 0.0605 Joules

6.  A book on a shelf 2m above the floor has a mass of 1.5kg. What is the gravitational potential energy of the book? GPE = mgh GPE = (1.5kg)(9.8m/s/s)(2m) GPE = 29.4 Joules

7.  Which runner has the greater kinetic energy: a 46kg runner moving at a speed of 8 m/s or a 92kg runner moving at a speed of 4 m/s? Runner 1 KE = ½ mv 2 KE = ½ (46kg)(8m/s) 2 KE= 1472 Joules Runner 2 KE = ½ mv 2 KE = ½ (92kg)(4m/s) 2 KE = 736 Joules

8.  If a 6kg box is moved from the floor to a storage compartment 2m above the floor, by how many joules does its potential energy change? GPE = mgh GPE = (6kg)(9.8m/s/s)(2m) GPE = 117.6 Joules

9.  The total energy of motion (KE) and position (PE) of any object is its mechanical energy (ME). FORMULA:ME = PE + KE  Sound energy is a form of mechanical energy. It involves the compression and expansion of air particles, thus has both kinetic and elastic potential energy.  The total potential and kinetic energy of all the microscopic particles in an object make up its thermal energy. This is also known as heat energy.

10.  Chemical energy is the energy stored in chemical bonds.  Electrical energy is the energy associated with electrical charges.  Electromagnetic energy is a form of energy that travels through space in the form of waves. This includes light energy, x-rays, microwaves, and other forms of electromagnetic waves.  Nuclear energy is energy stored in the nuclei of atoms (fission, fusion).

11.  The process of changing energy from one form to another is energy conversion.  Every energy conversion involves some conversion to thermal energy due to friction.

12.  When energy changes from one form to another, the total amount of energy stays the same.  The gravitational potential energy of an object is converted to the kinetic energy of motion as an object falls.