Section 1 review
There are many kinds of machines that we use everyday to do work or help us accomplish a task. All machines are fundamentally built up of combinations of six categories of simple machines: lever, pulley, wheel and axle, ramp, wedge, and screw. The mechanical advantage of a machine indicates how it changes the input force into an output force. The lever is a simple machine that multiplies force by the ratio of the input arm to the output arm. Read the text aloud
machine, simple machine, mechanical advantage, input force, output force, lever, fulcrum, input arm, output arm

MA= F o F i
M A lever = L i L o

Review problems and questions

  1. Is a car a machine? Is it a simple machine? Why or why not? Read the text aloud Show
  1. How are first-, second-, and third-class levers different? Read the text aloud Show
  1. The Mega-Rontastic Machine, resembling a fancy broom, is advertised on late-night television as a device to help you do household chores with less effort. Maximillian bought one and tested its mechanical advantage to see whether it actually worked as advertised. What measured values of mechanical advantage would justify the product claims about the Mega-Rontastic Machine? Read the text aloud Show
  1. Prince Ludwig II creates his own version of a machine that will lift a 25 kg bucket of water. Igor tries out the device and determines that, to lift the water by 2 m, he must pull the input rope by 10 m while applying 50 N of force. What is the mechanical advantage of Prince Ludwig II’s machine? (Assume that no energy is lost to friction.) Read the text aloud Show
  1. Astrid has two slotted masses and a meter ruler. She wants to hang the 100 g from one end of the meter ruler (at the 0 cm mark), hang the 300 g mass from the other end (at the 100 cm mark), and place the meter ruler on a knife edge to balance the lever. At what mark on the ruler should she place the knife edge? The mass of the ruler itself is negligible. Read the text aloud Show
  1. Zing is a safecracker who wants to lift a 150 kg safe full of loot, but he can only exert 490 N of force. He has a 60-cm-long steel rod as well as a rock he can use as a fulcrum.
    1. What minimum mechanical advantage does he need?
    2. How far from the safe should the rock be placed to provide this minimum mechanical advantage?
    3. What torque does Zing apply to lift the safe?
    4. What is the net torque about the fulcrum? Read the text aloud Show

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