1. 1. Friction – a force that acts like a brake on moving objects.
Chapter 8 : Machines
1. Friction – a force that acts like a brake on moving objects.

2. 2. Gear - ``a rotating wheel-like object with teeth around its rim; they are used to transmit force to other gears with matching teeth.

3. 3. Hydraulics – the study and technology of the actions and reaction of liquids at rest and in motion.

4. 4. Inclined Plane – a simple machine in the form of a slopping surface or ramp, used to move a load from one level to another.

5. 5. Lever – a simple machine, consisting of a bar and fulcrum, that can be used to increase force or decrease effort needed to move a load.

6. 6. Linkage – a system of levers used to transmit motion.

7. 7. Machine – a device that does some kind of work by changing or transmitting energy.

8. 8. Mechanical advantage – in a simple machine, the ability to move a large resistance by applying a small effort.

9. 9. Mechanism – a way of changing one kind of effort into another kind of effort.

10. 10. Moment – the turning force acting on a lever, determined by the effort times the distance of the effort from the fulcrum.

11. 11. Pneumatics – the study and technology of the characteristics of gases.

12. 12. Power –the rate at which work is done or the rate at which energy is converted from one form to another or transferred from one place to another.

13. 13. Pressure –the effort applied to a given area.

14. 14. Pulley –a simple machine in the form of a wheel with a groove around its rim to accept a rope, chain, or belt; it is used to lift heavy objects.

15. 15. Screw – a simple machine that is an inclined plane wrapped in the form of a cylinder.

16. 16. Torque- a measure of turning effort.

17. 17. Wedge – a simple machine that consists of two inclined planes placed back-to-back.

18. 18. Wheel and axle – a simple machine that is a special kind of lever; effort applied to the outer edge of the wheel is transmitted through the axel.

19. 19. Work - measurement of the amount of effort needed to change one kind of energy into another; the result of a force applied on an object and the object’s movement in the direction of the force applied on the object.