Presentation on theme: "Warm Up 1. What simple machine is a ladder? 2. What simple machine is an inclined plane wrapped around a pole? 3.What simple machine are steps. 4.What."— Presentation transcript:
Warm Up 1. What simple machine is a ladder? 2. What simple machine is an inclined plane wrapped around a pole? 3.What simple machine are steps. 4.What simple machine is a shark tooth? 5.What simple machine is a pair of scissors? 6.What simple machine is a mini blind? 7.What simple machine is a rake? 8.What simple machine is a nail? 9.What simple machine is a doorknob? 10.What simple machine is a baseball bat?
Simple Machines Science 7 Darren Nigh
A machine is a device that helps you do work
Simple Machines There are six types of machines that scientists call “simple machines.” All machines, no matter how large or complicated, are made up of combinations of these six machines: the incline plane, the wedge, the screw, the lever, the wheel and axle, and the pulley. WHEEL & AXLE
Incline Plane, Wedge and Screw
Incline Plane An incline plane is the simplest of all machines. It consists of a ramp or a similar wedge-shaped device, that makes doing work easier.
Inclined means tilted and plane means flat, so any tilted, flat surface is an inclined plane. A ramp, is an incline plane. The length of the plane is the effort distance, The height the plane is raised is the resistance distance.
Wedge A wedge is an incline plane that moves. Material is moved up an inclined plane, but a wedge is moved through material.
A nail is a wedge when hammered into a board, the pointed or sloping end of the nail moves through the material of the board. An axe is a wedge used for splitting wood.
Screw A screw is an inclined plane wrapped around a cylinder, forming spiraling ridges.
rotates, moves a certain distance into material. A screw rotates, and with each turn moves a certain distance into material.
pitch. The distance the screw moves depends on the screw’s pitch. the distance between the threads, The pitch is the distance between the threads, which are the ridges winding around the screw. pitch
The smaller the pitch, the smaller the distance the screw moves, but the greater the mechanical advantage of the screw. Thus a screw with a small pitch is easier to turn.
Levers, Wheel and Axle and Pulleys
Lever A lever is a bar that is free to rotate about a fixed point called the fulcrum. fulcrum
Levers are divided into three groups based on the location of the fulcrum, the resistance force and the effort force. Three groups of levers First Class Lever Second Class Lever Third Class Lever Resistance Effort Fulcrum
First Class Lever In a first class lever, the fulcrum is in-between the effort force and the resistance force. Effort Resistance Effort Fulcrum
Third Class Lever In the third class lever, the effort force is situated between the fulcrum and the resistance force. Effort Resistance fulcrum effort force resistance force Fulcrum
Second Class Lever Effort Resistance In a second class lever, the resistance force or load is situated between the fulcrum and the effort force. Example: Wheelbarrow The fulcrum is the wheel and the resistance (load) in a wheelbarrow is the object being moved while the person pushing the barrow supplies the effort. Fulcrum
Warm Up 1.What is an example of a third class lever? 2.Levers are divided into three groups based on what three criteria? 3. What is an inclined plane that moves? 4.The distance between the threads on a screw is known as _________ ? 5.What is an example of a second class lever? 6.T or F The smaller the pitch of a screw, the less of a mechanical advantage it will have. 7.The length of a plane is known as the ______ ? 8.What is an example of a first class lever? 9.The fixed point that a lever is free to move about is called a ____________. 10.What is the simplest of all machines?
Wheel and Axle A wheel and axle is a lever that rotates in a circle. They are made of parts that move in two circles: an axle, which moves in a small circle and the wheel, which moves in a larger circle.
load wheel (crank) axle The wheel is not always like a wheel on a car, For example, a screwdriver, a steering wheel and the crank in this diagram are examples of a wheel and axle machine. When you turn the wheel, your effort force moves in a larger circle than does the axle. The screwdriver is a wheel & axle, with the handle as the wheel.
Pulley A pulley is a lever that rotates around a fixed point. It is made of a wheel, usually grooved, that holds a cord.
Pulleys can be fixed or moveable attached to an unmovable object first class lever The fixed pulley is attached to an unmovable object such as a ceiling, and acts as a first class lever with the fulcrum being located at the axis but with a minor change, the bar becomes a rope. uses more effort than the load to lift A fixed pulley is the only pulley that when used individually, uses more effort than the load to lift the load from the ground. Fulcrum Fixed Pulleys
Moveable Pulleys A movable pulley is a pulley that moves with the load. The movable pulley allows the effort to be less than the weight of the load. The movable pulley also acts as a second class lever. The load is between the fulcrum and the effort. The advantage of a movable pulley is that you use less effort to pull the load. The disadvantage of a movable pulley is that you have to pull or push the pulley up or down. The pulley and the load move up The pulley and the load move down
Block and Tackle Pulley System Uses more than one moveable pulley to reduce the amount of force needed to lift a load. The more pulleys that are used, the smaller the applied force but the farther the rope must be pulled to move the load a certain distance.
Cool Down Review 1.Levers are divided into three groups based on what three criteria? 2.The length of a plane is known as the ______ ? 3.The fixed point that a lever is free to move about is called a ____________. 4.The distance between the threads on a screw is known as _________ ? 5.The larger the (above) of a screw, the (less/more) of a mechanical advantage it will have. 6.What is the advantage and disadvantage of a movable pulley. 7.What simple machine is an inclined plane wrapped around a pole? 8.Name the six simple machines 9.The height of an inclined plane is the ___________. 10.Effort force, resistance force, or fulcrum, which is in the middle of a third class lever?