Goal 7  Students will solve for work in the equation work = force X distance and will recognize that force and distance must act in the same direction to produce work.    Part 1 - Solving for Work Part 2 - relationship between work and distance

What is work? Think about it. What does work mean to an 8th grader. In scientific terms it means you exerted a force on an object to move it some distance. Work is done on an object when the object moves in the SAME distance in which the force is exerted. If the object does NOT move in the direction your applied the force, no work was done.

Is work being done, Yes or No   Yes No No

DO WORK! To do work, the force you exert MUST be in the same directions the object  moves.

https://www.youtube.com/watch?v=iCqm5uxc2dE

How to calculate work W = work Joule F = force Newton D = distance Meter

The unit for work is Joule (J)

What's a Joule? A joule is the amount of energy required (or work performed) when applying a force of 1 newton (1 newton = 0.2248 pounds) over a distance of 1 meter. There is a famous legend about apples falling on Isaac Newton's head, and a small apple weighs roughly one newton. So think of a joule as roughly the energy required to lift an apple from the floor to a table, roughly 1 meter. Read more at Suite101: What are Calories, Joules, BTUs, and Ergs: Units To Measure Energy and Work in Physics and Other Sciences http://www.suite101.com/content/what-are-calories-joules-btus-and-ergs-a120457#ixzz1JyLcFQoQ

Sample Problem Calculate work: W = F x d W = 50 Newtons x 10 Meters W = 500 Newton x Meters = 500 Joules W = 500 J

Power – How quickly work was done Power = work done/time needed Unit is the Watt Work Power Time

1) How much power does it take to do 450 J in 5 sec? Work = 450 J Time = 5 Sec Power =450/5 Power = 90 Power = 90 Watt Work Power Time

A Machine any device that makes doing work easier. Input force – force exerted on a machine. Output force – the resistance force, or the work a machine does to move an object over some distance.

NO MATTER WHAT TYPE OF MACHINE, THE OUTPUT WORK IS NEVER GREATER THAN THE INPUT WORK. Object Output Work iInput Work

Mechanical Advanyage (MA) – ratio of times the output force is to the input force. No units. MA is always a ratio. http://www.youtube.com/watch?v=yhzMYHiuEC4&feature=player_detailpage

Problem 1 – A wheelbarrow has a mechanical advantage of 2. 2 Problem 1 – A wheelbarrow has a mechanical advantage of 2.2. The output distance

Goal  Students will solve for work in the equation work = force X distance and will recognize that force and distance must act in the same direction to produce work.