I.P.C. 4 D Investigate and Demonstrate Mechanical Advantage and Efficiency of various machines such as levers, motors, wheels and axles, pulleys and ramps

Percentage Efficiency of Machines! 100%????

You will never have a machine that is 100% efficient You will never have a machine that is 100% efficient. Some energy almost always is lost as heat. (Called dissipated)

Machines: Change the size and/or direction of a force.

Efficiency- in science it is the amount of work you get out of a system as compared to how much you put into it. WO %E WI

When solving a problem--- First read the problem carefully and list what you know and what you are solving for. Second identify the formula from the formula chart that includes what you are given.

Calculate !!! What is the efficiency of a machine that requires 110 J of input energy to do 35 J of useful work? Solving for efficiency…what is the input and output? Calculate and multiply by 100!

What is the efficiency of a machine that requires 110 J of input energy to do 35 J of useful work? E=35J/110J E= .32 Don’t forget to multiply by 100 Efficiency is 32% Wo = 35 J WI = 110 J

What is the efficiency of her body when a cyclist expends 1000 J of work to deliver mechanical energy to the bicycle at the rate of 100 J?

Pulleys-The MA of a pulley is equal to the number of supporting ropes What is the Mechanical Advantage for each of the following pulleys? MA=4 because there are 4 supporting ropes. It makes it four times easier to lift the bucket MA=2 because there are 2 supporting ropes. It makes it two times easier to lift the bucket

Mechanical Advantage and Efficiency are NOT the same thing!! Machines can make make work easier to do but still not ever be 100% efficient. Stairs increase mechanical advantage because they make it easier to climb a slope but they are not 100% efficient.

Lever: simple machine, bar that turns about a fixed point (fulcrum) Crowbar Seesaw

3 types of levers:

A lever can multiply forces No machine can multiply work or energy… A lever can multiply forces No machine can multiply work or energy…. We may put 100 J of work onto a lever but only get 98 J of work out. The lever is said to be 98% efficient.

10÷2 = 5x easier to lift 100 kg ball To find the MA of a lever, divide the effort arm length by the resistance arm length. MA = effort arm length / resistance arm length 10÷2 = 5x easier to lift 100 kg ball 10 cm Effort Arm Effort or Lift here 2 cm Resistance Arm The longer the effort arm, the higher the MA or the easier it makes the work seem.

Hint: Look at the length of the effort arm Which lever requires the least effort to lift a load? TAKS-2006 Hint: Look at the length of the effort arm MA = effort arm length ÷ resistance arm length

Which lever arrangement requires the least effort force to raise a 500 N resistance? TAKS-2004

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