In other words, energy cannot be created or destroyed… <ul><li>Unless work was done on the system, the total energy of the system does not change. </li></ul>
… it can, however, be converted between different types. For example, PE can be transferred to KE!
Work is being done against friction and gravity. <ul><li>input energy (chemical energy) > output energy (thermal energy) </li></ul><ul><li>energy is lost to friction </li></ul>
If there is no gain in internal energy and no work done against friction, Q=0
The body transfers the chemical energy which is released as kinetic energy of the ball. <ul><li>The input of energy is chemical energy from the ice cream. </li></ul>But the total energy remains the same! Example:
A roller coaster, is pulled up to point A where it and its screaming occupants are released from rest. Assuming no friction, calculate the speed at points B , C and D . ( h a = 35 m, h d = 12 m, h c = 22 m) Problem:
We will find the velocity at point C and show you step by step how to find it. At the end of the presentation, you can solve for the other points in the problem and check your answers with ours.
Step 1: Write/Draw Knowns and Unknowns h a = 35 m h d = 12 m h c = 22 m V a = 0 m/s V b = ? V c = ? V d = ? m = / *mass is irrelevant because it cancels out in the equation
Step 2: Identify Types of Energy <ul><li>A: PE, because it is at rest and at its highest point </li></ul><ul><li>C: PE, because it has height and KE because it has velocity </li></ul>