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# How do they relate to work and energy?

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How do they relate to work and energy?
Simple Machines How do they relate to work and energy?

Do Now (2 minutes) Place your bags at a desk. Form groups of 3 at a lab station. How much force is required to lift a 1kg object at a constant speed? How much work is done by a machine that lifts a 1kg mass to a height of 10 cm?

Today’s Schedule By the end of the day you should be able to:
Identify 3 ways simple machines simplify a task Calculate the mechanical advantage of simple machines Understand why the work performed by a machine cannot exceed the energy input Schedule: Complete the Simple Machines investigation Share and Discuss our results Complete Exit-Ticket HW Assignment: (p ) 79, 80, 81, 82

Directions Each group will investigate two simple machines:
Complete steps 1-4 or Machine #1 (8 minutes) When signaled, move to the next station and repeat steps 1-4 for Machine #2 Move to a desk and complete questions 1-3

Six Simple machines

Machines Mechanical Advantage is the ratio of the resistance force to the effort force Resistance Force: Force exerted by the machine Ex: The lever on the object Effort Force: force exerted by you Ex: You on the the lever.

Simple machines cannot:
Change the magnitude of a force required to do work. Change the direction of the force to suit the user’s needs. Change the speed in which work is done. Simple machines cannot: Reduce the amount of work required to complete a task.

The law of conservation of energy applies to all machines
The law of conservation of energy applies to all machines! At the same time we do work on one end of the lever, the other end does work on the load.

EFficiency Efficiency: the ratio of the output work to the input work
Win = Fin din =(5.5 N)(20 cm) Wout= Fout dout = (10 N)(10 cm)

Today’s Schedule By the end of the day you should be able to:
Identify 3 ways simple machines simplify a task Calculate the mechanical advantage and efficiencies of simple machines Understand why the work performed by a machine cannot exceed the energy input Schedule: Complete the Simple Machines investigation Share and Discuss our results Complete Exit-Ticket HW Assignment: (p ) 79, 80, 81, 82

Exit ticket Don’t forget HW! : (p.290-291) 79, 80, 81, 82
Identify 3 ways machines make it easier to perform a task. Don’t forget HW! : (p ) 79, 80, 81, 82 Placet ticket and classwork in the basket by the door.

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