A wheel and axle consists of two disks or. Examples are a steering wheel and shaft, a car wheel and axle, and a screwdriver. An inclined plane is a slanted surface on which a force can move an object to a different elevation. Why do gentler slopes and ramps require less energy to move a load on? Because the input force required to travel the greater distance of a slope is changed to the smaller distance of the output force — the upward motion.
A wedge is a device made of two back to back inclined planes and is used to split objects. When a wedge is driven into a log, the size of the input force at the wider top of the wedge is changed to greater output force at the narrower point forcing the wedge through the wood. Knife blades are an example of a wedge. A screw is an inclined plane wrapped around a cylinder. Screws with threads closer together require.
Nuts and bolts are screws. However, if we were to use two pulleys — one attached to the overhead beam, and the other attached to the weight — and we were to attach one end of the rope to the beam, run it through the pulley on the weight and then through the pulley on the beam, we would only have to pull on the rope with 50 lbs. Again, we have traded increased distance for decreased force. If we want to use even less force over an even greater distance, we can use a block and tackle.
According to course materials from the University of South Carolina, "A block and tackle is a combination of pulleys which reduces the amount of force required to lift something. The trade-off is that a longer length of rope is required for a block and tackle to move something the same distance. As simple as pulleys are, they are still finding use in the most advanced new machines.
For example, the Hangprinter , a 3D printer that can build furniture-sized objects, employs a system of wires and computer-controlled pulleys anchored to the walls, floor, and ceiling.
Many devices use screws to exert a force that is much greater than the force used to turn the screw. These devices include bench vices and lug nuts on automobile wheels. They gain a mechanical advantage not only from the screw itself but also, in many cases, from the leverage of a long handle used to turn the screw.
According to the New Mexico Institute of Mining and Technology, "Wedges are moving inclined planes that are driven under loads to lift, or into a load to split or separate. For example, if we want to split a log, we can drive a wedge downward into the end of the log with great force using a sledgehammer, and the wedge will redirect this force outward, causing the wood to split.
Another example is a doorstop, where the force used to push it under the edge of the door is transferred downward, resulting in frictional force that resists sliding across the floor. Find some fun activities involving simple machines at the Museum of Science and Industry in Chicago.
Live Science. Ask: Is doing homework work by this definition? No, homework is not work. Pushing a book across a desk is work because you are applying a force a push on a book for a certain distance the length of the desk. You are not pushing homework anywhere. Imagine that you want the same amount of work to get done using less force. If you use half as much force to push the book, then you will have to push the book twice as far to do the same amount of work.
Or, you could use a simple machine to make up the difference in the force you are applying. Explain that people often use simple machines to make work easier.
Introduce the class to the names of various simple machines and show them a picture of each from the Simple Machines photo gallery: levers, the wheel and axle, pulleys, screws, and inclined planes. Tell the class simple machines make work easier by increasing mechanical advantage. Tell students that an example of mechanical advantage is using the claw of a hammer to remove a nail.
A small force applied to the handle of the hammer produces a greater force at the claw end of the hammer, allowing for the removal of stubborn nails. Explain that complicated machines, such as robots and cars, are made up of combinations of simple machines and other parts. Robots are complex machines that contain many simple machines. Some examples of simple machines that are used in robot construction are wheels and axles for mobility, allowing robots to move from place to place, and robot arms, which are levers, enable them to manipulate objects.
Explain that students are going to try simple experiments with simple machines, and then use those simple machines to solve challenges. Construct a lever by taping a marker parallel to the edge of the table. Tear off a piece of masking tape, loop it, and attach it to the end of the ruler. Place the ruler on the marker at the center point, like a seesaw, and then press a tennis ball firmly to the tape.
Invite a student volunteer to demonstrate the lever; first, have the student gently lift the ball by applying force to the end of the lever ruler opposite the ball. Second, instruct the student to reposition the lever ruler so the ball is as close to the fulcrum marker as possible.
Have the student press the lever again to lift the ball. Lastly, reposition the lever ruler so the ball is as far away from the fulcrum marker as possible while still leaving a portion of the lever ruler to be pressed down. Have the student press the lever to lift the ball again.
A photo of each lever situation is available in the Simple Machines Demonstrations photo gallery. Discuss what the class saw and what the volunteer observed. Ask: Which lever configuration made the ball easiest to lift? Which lever configuration made it the most difficult to lift the ball?
Which lever configuration moved the ball the farthest from its starting position? How does the lever provide a mechanical advantage when moving the ball? Introduce the lever challenge. Explain that each group will attempt to move a tennis ball from the table to the center of a roll of masking tape at varying distances. Introduce the rules. Hands may not be used to move the ball to the goal, but hands may be used to place the ball on the lever and to operate the lever. Nothing may be used to secure the ball to the lever.
The marker may not be moved from the edge of the table. The masking tape roll may not be moved unless the teacher instructs it. The winner will be the group that moves the ball to the center of the masking tape roll from three different distances with the least amount of attempts. Separate the class into groups of While these are certainly some examples of machines, devices as simple as hammers and screws are also machines. Why are simple tools like hammers and screws considered to be machines?
Because like all machines, they also change forces and make work easier. A machine is any device that makes work easier by changing a force. A machine can do this by increasing the output force, or by increasing the output distance, and sometimes by changing the direction of the input force.
Work is done whenever a force moves an object over a distance. Output force vs Input force : When we use a machine, we apply force to the machine. This force is called the input force. The machine, in turn, applies force to an object. This force is called the output force. The output force may or may not be the same as the input force.
Output distance vs Input distance : The force we apply to the machine is applied over a given distance, called the input distance. The force applied by the machine to the object is also applied over a distance, called the output distance. The output distance may or may not be the same as the input distance.
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