Do Now

Write a one-paragraph answer in your science journal to the following question:

Why do we use machines?

Big Picture

Motion energy is properly called kinetic energy; it is proportional to the mass of the moving object and grows with the

square of its speed. (MS-PS3-1)

Objectives: Explain how a machine makes work easier.Calculate mechanical advantage.Identify the simple machines that make up a compound machine.

Learning TargetToday I will: learn how machines make work easier.So that I can: understand how machines improve working conditions.I will know I got it if: I can explain how machines make work easier with specific examples.

Agenda

Today we will:

Complete a do now.

Learn about machines with a teacher presentation.

Begin a lab write up.

Exit ticket

Vocabularymachinemechanical

advantage

https://www.youtube.com/watch?v=WUt_VJQ8WCw&feature=player_embedded

Machines: Making Work Easier

• A machine is a device that makes work easier by changing the size or direction of a force.

Machines: Making Work Easier, continued

• Work In, Work Out The work that you do on a machine is called work input. The work done by the machine on an object is called work output.

• How Machines Help Machines allow force to be applied over a greater distance, which means that less force will be needed for the same amount of work.

Machines: Making Work Easier, continued

• Same Work, Different Force Machines make work easier by changing the size or direction of the input force.

• The Force-Distance Trade Off When a machine changes the size of the force, the distance through which the force is exerted must also change.

Mechanical Advantage• What Is Mechanical Advantage? A machine’s mechanical advantage is the number of times the machine multiplies force.

• Calculating Mechanical Advantage You can find mechanical advantage by using the following equation:

( )mechanical advantage MA = output force

input force

Mechanical Efficiency

• The less work a machine has to do to overcome friction, the more efficient the machine is. Mechanical efficiency is a comparison of a machine’s work output with the work input.

• Calculating Efficiency A machine’s mechanical efficiency is calculated using the following equation:

mechanical efficiency =work outputwork input

100

Mechanical Efficiency, continued

• Perfect Efficiency? An ideal machine would be a machine that had 100% mechanical efficiency.

• Ideal machines are impossible to build, because every machine has moving parts. Moving parts always use some of the work input to overcome friction.

Inclined Planes

• An inclined plane is a simple machine that is a straight, slanted surface.

• Mechanical Advantage of an Inclined Plane The mechanical advantage (MA) of an inclined plane can be calculated by dividing the length of the inclined plane by the height to which the load is lifted.

Exit Ticket

How do machines make work easier?