Machines make work (the application of a force to move an object) easier. Machines enable us to increase a force and speed of an object; machines enable us to change the direction and location of an object. A machine does work by increasing a force (push/pull) on an object. Machines are concerned with two forces-the effort force (push or pull we apply) and the resistance force (weight of the object being moved). Furniture movers do work when they move boxes; gardeners do work when they hoe weeds. Machines make this work easier. Furniture movers use a ramp to slide the boxes onto a truck;a gardener uses a shovel to dig out the weeds. The ramp and the shovel are simple machines and make moving boxes and pulling weeds easier. There are six types of simple machines that make work easier.
Levers help us move and lift objects. All levers (or bars), regardless of shape, have three parts.
1. Fulcrum-the point at which a lever swings, turns, or balances on.
2. Effort-force (push/pull) we apply
3. resistance- the object/load we want to move or lift.
Levers are divided into three categories
1. First Class- the fulcrum is located between the effort force and the load. Example: crow bar, see saw, hammer. With a hammer, the effort is the push or pull on the handle, the load is the claw that grasps the nail to be taken out of the wood, and the fulcrum is the head of the hammer which swings and turns as you push the hammer to take out the nail. First class levers work best when the fulcrum is near the resistance/load. Try the discovery activity in you science book on pg. 274 "Move Those Loads: Making and Using a Lever"... It works! This is an animation of a see saw lever from discover.edventures.com
2. second class- The load is located between teh fulcrum and effort. Example: wheelbarrow. The effort is the push we apply on the handles, the load is the bucket full of stuff, and the fulcrum is the will which allows lift and movement for transport.
3. third class- The effort is between the load and fulcrum. Example: broom. The fulcrum is the handle which swings as we apply force. the load is the dirt we sweep.
A pulley helps us lift and move stuff. A pulley is a rope around a wheel with a groove along its edge to hold the rope. You would pull the rope down on one side of the pulley to move or lift a weight on the other side of the rope. There are two types of pulleys...
1. fixed or in place pulley- good to move stuff but doesn't make it easier to lift heavy stuff. It acts as a first class lever with the fulcrum located at the axel. It doesn't make lifiting easy because the fulcrum and distance from the load is equal. Remember: levers work best when fulcrum is closer (not equal) to the position of the load. Example of a fixed pulley is a flag pole.
2. movable pulleys reduce the amound of force needed to lift a load. It works as a second class lever, moves the load, and has mor ropes. picture of a fixed pulley from kosmoi.com
Wedges are double inclined planes. Wedges push under or into the load. Wedges work best when it is long and thin. Examples of wedges include axe, nail, needle. image found at staff.harrisonburg.k12.va.us
An inclined plane is a slanted surface/higher on one side and lower on the other side. An inclined plane makes moving heavy objects easier. This surface allows one to apply only a small amount of force to move a heavy object over a longer distance. Inclined planes work best when they are longer. Examples include a ramp and staircase. image found at kosmoi.com
A screw is an inclined plane wrapped around a cylinder. Screws hold things together. Examples of screws include the jar and lid, screw. image from www.harmsco.com
A wheel and axle helps move things, lift things, and speed things up. A wheel is attached to a handle that turns in the same direction. Examples include bicycle pedals, door knob, and screwdriver. With a screw driver, the handle is the wheel portion which moves with a push, and the shaft/bar is the axle.
More examples of simple machines we use everyday
Activities with simple machines
