1. Lesson 1 How do machines help people work? Using force in order to move an object a certain distance. Work is measured in an unit called joule (J). W= F X D Multiply the force and distance to measure work.

2. Work and Machines Machine Any device that helps people do work. Simple Machines Made of one or two parts. Nail clippers and chopsticks. Compound Machines Cars, trucks, airplanes. Has one or more simple machines among its parts.

3. How machines help They make it easier to work A car jack and a crowbar are examples of machines that increase the amount of force to lift or move an object Other machines change the distance over which force must be applied.

4. Machines and Friction Not all the energy you put into machine is used to do work because some energy is lost due to friction. Friction is created when the moving parts of a machine rub together. There are ways to reduce friction. Using wheels and rollers. Friction creates heat and slows down machine´s parts. Coating the machine parts with grease , oil or wax.