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# Work and Energy

### Study for Chapter 9 Work and Energy

Question | Answer |
---|---|

What is work? | Transfer of energy. Equation is W=F*D |

What is the unit for work? | Joule One Joule = One Newton * One Meter |

For work to be done the force and motion must be in the ________ line | same |

If a force is applied to an object and it moves in a direction opposite to the direction of the force, _________ work is done. | negative |

If someone carries a 150 N object to a table for a distance of 10 meters, why is no work done? | The motion and the applied force have to be in the same line. |

What does it mean to say that force and motion are in the same line? | They are either in the same or opposite direction as each other. |

How is power calculated? | Work/Time. |

What's the formula for work | w=f*d |

Sam has to use 250 N of force to move the piano 10 meters. How much work has been done to the panio? | 2500J |

What is kinetic energy? | The energy of motion. |

What is the formula for kinetic energy? | KE=1/2mv^2 |

What is mechanical energy? | the sum of potential energy and kinetic energy |

What energy is stored energy that has not been used yet? | Potential Energy |

What is the equation for Velocity when using only mass and kinetic energy? | V = √(2KE / M) |

Potential and Kinetic energy are measured in what unit? | Joules |

When playing the game of football what is your potential energy as a lineman | When playing football as a lineman your potential energy is when you are in your stance and then you release your energy when you hit the other players. |

What is mechanical energy measured in? | joules |

Stretching or compressing a spring is an example of ________ | elastic potential energy |

What is the equation for kinetic energy | Kinetic Energy= 1/2 * m * v^2. |

What happens to the kinetic energy when the mass gets doubled | the kinetic energy would double. |

What kind of potential energy would you have if you were standing on top of a staircase? | gravitational potential energy |

What would happen to the kinetic energy if you doubled the mass of an object that had 40 Joules of kinetic energy? | The new kinetic energy would be 80 Joules |

What would happen if you doubled the velocity of an object that had 25 joules of kinetic enrgy? | The new kinetic energy would be 100 Joules |

Machines make work ____ not less | easier |

What are the two types of mechanical advantage? | actual mechanical advantage and ideal mechanical advantage |

How is the Mechanical Advantage of a Wheel & Axle Determined? | the formula is the ratio of the radius of the wheel to the radius of the axle. |

What is mechanical advantage? | a measure of how many times a machine multiplies your effort(input force). |

What are some examples of third class levers? | Tweezers. Mouse Traps. and Nail Clippers. |

Define pulley | a kind of lever that can be used to change the direction of a force and / or multiply tthe input force |

What is the mechanical advantage of a fixed pulley? | One |

What is the mechanical advantage of one fixed and one movable pulley | two |

What is a fulcrum? | It is the pivot point of a lever |

How many classes of levers are there? | Three |

How is mechanical advantage related to the total number of pulleys in the pulley system? | The number of pulleys equals the mechanical advantage. |

What is the equation for Mechanical Advantage when dealing with distance? | input distance/output distance |

Explain the three classes of levers. | Class 1:The fulcrum is between the load and the effort.Class 2:The load is between the fulcrum and the effort.Class 3:The effort is between the fulcrum and the load. |

What is the equation for Mechanical Advantage when dealing with distance? | input distance/output distance |

How many different classes of levers are there? | Three |

What is an example of a class 3 lever? | a broom |

What is the equation for efficiency? | E =work out divided by work in |

Why is it impossible for a machine to 100% efficient? | Some of the input work is always lost to friction |

What is a by-product of friction? | Heat (thermal energy) |

If an inclined plane is 6 meters long and 2 meters high, how much force would you have to exert to move a 900 N box up the plane? | 300 N (MA = 6/2 = 3)..Input Force = Output Force/MA...IF = 900N/3 = 300N |

If a marble has a mass of .15kg and is at a height of 50 cm, how much GPE does it have? | 0.735 Joules PE =mgh g= 9.8 h= 0.5 meters m= 0.15 kg |

For a first class lever, where should the fulcrum and effort be placed to make it the easiest to lift a load? | The fulrum should be as close to the load as possible and the effort should be as far away from the fulcrum as possible |

if a simple machine reduces the amount of force you have to apply, what is the the "cost" of using the machine? | You have to exert your lower force over a longer distance! |