Mechanical Advantage & Effeciency

Objectives Explain how a machine makes work easier Describe and give examples of the force-distance trade-off that occurs when a machine is used Describe & Calculate mechanical advantage Describe & Calculate effeciency Explain why machines are not 100% efficient

What is a machine? Machines make work easier by Changing the amount of ___________ you exert Changing the __________ over which you exert the force Changing the __________ the force is exerted

Which is easier? Opening a paint can with your fingers? Opening a paint can with a screwdriver? OR

Which is easier? Pushing a heavy box up a ramp into a truck? Lifting a heavy box into a truck? OR

When using a machine to do work, two forces are involved. _________ Force (Fin) The force ____ apply to the machine in doing work (Win) __________ Force (Fout) The force that the _________ applies in doing work (Wout)

Two types of work are involved. Work input is the amount of work done _____ a machine. Input force x input distance Work output is the amount of work done _____ a machine. Output force x output distance How are the two related?

Force-distance trade-off To ________ the force needed, increase the ____________ To _______ the force needed, decrease the ____________ Examples: wheelbarrow and hammer

Force-Distance Trade-off (increases force) Wheel barrow ________ in a greater distance (lift handle of wheelbarrow) _________ applied a shorter distance (load in wheelbarrow lifted)

Force-Distance Trade-off (decreases force) Hammer _____________ applied over a short distance _____________ applied over a long distance

Measuring the benefits: Mechanical Advantage Mechanical Advantage tells you how many times the machine ____________ the force. a machine with a large mechanical advantage can make lifting a heavy load easier Actual Mechanical Advantage Ideal Mechanical Advantage

Calculating Mechanical Advantage What is the mechanical advantage of a machine that applies 200N to an object when you apply 50N to the machine? Equation

Calculating Mechanical Advantage You apply 2000 N to a machine and the machine applies 200 N to an object. What is the mechanical advantage? Equation MA = (Fout)/(Fin) MA = (200N)/(2000N) MA = 0.1

Calculating Mechanical Advantage You apply 10 N to a machine and the machine applies 10 N to another object. What is the mechanical advantage. Equation

Mechanical Advantage:What does it mean?

However, some output work is lost due to ___________. Efficiency We said that the input work _________ the output work, or: Win = Wout However, some output work is lost due to ___________. The comparison of work input to work output is called ___________________. No machine has ______ percent efficiency due to friction. What would improve the efficiency of a machine? (Hint: What reduces friction?)

Calculating Efficiency How efficient is a machine that takes 40 J of work and produces 30 J of work? Equation

Calculating Efficiency You do 250,000 J of work to cut a lawn with a hand mower. If the work done by the mower is 200,000 J, what is the efficiency of the lawn mower? Equation