Review of Chapter 4 Book “M”

Section 1 What is work? Work is done on an object when the object moves in the same direction in which the force is exerted. How do you find work? Work = Force X Distance

Section 1 Continue What is power? Power is the rate at which work is done. How do you calculate power? Power = work/time or power = (force X Distance)/time

Section 2 What is a machine? Machine is a device that allows you to do work in a way that is easier or more effective What is input force? The force you exerts on the machine. Also know as the effort force What is the output force? The force the machine exerts on an object. Also know as the resistant force

Section 2 Continue What is input work? Input force time the input distance What is output work? Output force time the output distance What are the three ways a machine can make work easier? Changing force, changing distance, and changing direction

Section 2 Continue What is Mechanical Advantage? A comparison of the input force to the output force or the number of times a machine increases a force exerted on it. How do you find? MA = output force/input force

Section 2 Continue What is efficiency? The efficiency of a machine compares the output work to the input work. How do you find efficiency? Efficiency = (output work/input work) X 100% What is the difference between ideal and real machines? Ideal machines have 100% efficiency and only exist on paper, and real machines lose some work due to friction, thus always having less than 100% efficiency.

Section 3 What are the 6 basic kinds of simple machines? Inclined plane, wedge, screw, lever, wheel and axle, and pulley What is an incline plane? Incline plane is a flat, sloped surface What is the ideal mechanical advantage of an incline plane? IMA = length of incline/height of incline

Section 3 continue What is a wedge? A device that is thick at one end and tapers to a thin edge at the other end How do you find the mechanical advantage? IMA = Length/width What is a screw? A screw can be thought of as an incline plane wrapped around a cylinder How do you find the mechanical advantage of a screw? IMA = length around the threads/length of the screw

Section 3 continue What is a lever? A rigid bar that is free to pivot, or rotate, on a fixed point What are the three types? First-class, second-class, and third-class How do you find the mechanical advantage of a lever? IMA = distance from fulcrum to input force(or effort distance)/Distance from fulcrum to output force(or resistant distance)

Section 3 continue What is a wheel and axle? A simple machine made of two circular or cylindrical objects fastened together that rotate about a common axis. How do you find the mechanical advantage? MA = radius of wheel/radius of axis

Section 3 continue What is a pulley? A simple machine made of a grooved wheel with a rope or cable wrapped around it. What are the three types? Fixed pulley, movable pulley, and block and tackle What is the mechanical advantage? IMA = number of sections of rope that support the object.

Section 3 continue What is a complex machine? A machine that utilizes two or more simple machines How do you calculate the mechanical advantage? IMA = the product of the individual IMA of simple machines that make it up.