A machine is… • A device that allows for easier and more effective work. • Something that does not have to be complex. • Something that does NOT decrease the amount of work that is done. So what exactly is a machine?
What do machines do to make work easier? • Machines change the amount of force YOU exert • Machines change the distance over which you exert your force. • Machines multiply either force or distance, or they change direction.
Input and Output Forces • Input force, sometimes called an effort force, is the force that you (the operator) exert on the machine • Output force, also known as resistance force, is the force exerted by the machine
Making your life easier! • The output force is ALWAYS larger than the input force. • Ask yourself… “What’s Easier?”
Which would you rather do? Lift a car… Or roll it up a ramp…
Multiplying Distance • When we multiply distance, the output force is greater than the input force. • Applying a force over a short distance: Your hands move a short distance and the bat moves a longer distance.
Neither force nor distance is multiplied Would you rather push and lift the blinds up or pull the string down to raise the blinds?
Mechanical Advantage • Also known as MA • Mechanical advantage- the number of times a force is exerted on a machine is multiplied by the machine Mechanical Advantage = Output Force Input Force • The equation compares input force versus output force
Ideal vs. Actual Advantage • Ideal MA = Expected MA • Actual MA = Expected MA – Friction … Will we ever have Ideal Mechanical Advantage?
So why can’t the ideal mechanical advantage ever be equal to the actual mechanical advantage? Friction Energy is converted to heat.