In this lesson, students use simple machines to explore the relationship between forces and motion. They focus on how people can use levers to make work easier, investigating how the structure of the lever affects how much work it can do.
Prepared hands-on materials, full year grade-specific curriculum, and personalized live professional development designed to support mastery of current state science standards.
Sewing for Football Players
Marge Switzer sews many football jerseys. Marge is the seamstress for the Green Bay Packers. The Packers are the football team of Green Bay, Wisconsin.
Marge has a sewing room across from the locker room. One of her jobs is to mend the players’ uniforms. She fixes rips or tears that occur during the game.
As a seamstress, Marge uses different tools to help her do her job. One tool is a good pair of scissors. Many people don’t think of scissors as machines, but they are. In science, a machine is any device that does work. Work is any change in position, speed, or state of matter due to force.
Forces on Earth
Remember that a force is a push or pull that acts on an object. Force is always needed to transfer energy into or out of a system.
Gravity is a kind of pulling force. Gravity is the force of attraction between all matter. On Earth, the force of gravity pulls all objects near Earth’s surface down.
Gravity is why a football thrown by a player will fall back to the ground. It is also why we don’t all float off into space.
Friction is another force that slows motion whenever two objects rub against each other. Friction slows motion because it causes some of the energy of the moving object to change into heat.
Forces on Earth
Remember that a force is a push or pull that acts on an object. Force is always needed to transfer energy into or out of a system.
Gravity is a kind of pulling force. Gravity is the force of attraction between all matter. On Earth, the force of gravity pulls all objects near Earth’s surface down. Gravity is why a football thrown by a player will fall back to the ground. It is also why we don’t all float off into space.
Friction is another force that slows motion whenever two objects rub against each other. Friction slows motion because it causes some of the energy of the moving object to change into heat.
Simple Machines Help Do Work
To understand how scissors use force to do work, we need to begin with their structure. Scissors are made up of two smaller simple machines. A simple machine is any device that helps us do work by redirecting force.
We’ll use a seesaw to explore this idea further because seesaws are similar to scissors. Both seesaws and scissors use levers to do work. A lever is a simple machine that is made up of a stiff beam that rests on a support called a fulcrum. The beam is called an arm.
Scissors are made up of two levers. Seesaws are one lever. They have a simple structure. A long, narrow board is supported by the fulcrum in the middle of the board.
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