1. Machines Section 10.2 Physics

2. Objectives Demonstrate knowledge of why simple machines are useful. Communicate an understanding of mechanical advantage in ideal and real machines. Analyze compound machines and describe them in terms of simple machines. Calculate efficiencies for simple and compound machines.

3. Simple Machines Machine: eases the load by changing either the magnitude or the direction of a force as it transmits energy to the task. 6 Simple Machines.

4. Simple Machines Pulley Lever Wedge Inclined Plane Screw Wheel and Axle

5. Compound Machines Compound Machine: two or more simple machines linked so that the resistance force of one machine becomes the effort force of the second.  Ex. Bicycle.

6. Mechanical Advantage Both simple machines and compound machines supply a mechanical advantage. Mechanical Advantage: The ratio of resistance force to effort force. (MA) MA = F r /F e

7. Mechanical Advantage Some machines have a mechanical advantage greater than 1. If an MA is greater than one, the machine increases the force you apply and makes work easier.  Ex. Bottle opener.

8. Mechanical Advantage The mechanical advantage of a pulley is equal to one. How does it help you?  The arrangement of the pulley system changes the direction of the force applied.

9. Mechanical Advantage Mechanical Advantage Equations on Equation wall.

10. Machines and Efficiency Even though machines make work easier, no machine is 100% efficient. Efficiency: ration of output work to input work. In a non-ideal machine, work out-put can never exceed work in-put.

11. Efficiency Eff. = (W o / W i )(100) Eff. = (MA / IMA)(100)

12. Practice Problems Page 238. 13-16.