Machine Efficiency and Energy Losses

Try these questions

5 questions from this lesson’s quiz. Start the lesson to answer them and see the right answers.

1. 1. A pulley system used to lift a water tank at a farm in Nyeri has a velocity ratio of 5. An effort of 120 N is needed to lift a load of 420 N. Calculate the efficiency of the pulley system as a percentage.

   Type your answer (in %) in the lesson.

2. 2. Why does adding grease to a pulley axle increase its efficiency without changing its velocity ratio?

   • A. It reduces friction, so less effort is wasted as heat and the mechanical advantage rises, while the VR depends only on the machine's dimensions
   • B. It makes the load lighter, so a smaller effort is needed
   • C. It increases the distance moved by the effort, so the VR rises
   • D. It removes the weight of the pulley, so the machine becomes 100% efficient

3. 3. A real machine has an efficiency of less than 100%. Into which forms is most of the wasted input energy transformed?

   • A. Chemical energy and nuclear energy
   • B. Heat energy and sound energy
   • C. Gravitational energy and elastic energy
   • D. Light energy and magnetic energy

4. 4. What term is used for the percentage ratio of useful work output to total work input of a machine?

   Type your answer in the lesson.

5. 5. A worker in Eldoret pulls a 600 N sack up a ramp 5 m long with an effort of 200 N along the ramp. The sack is raised through a vertical height of 1.5 m. What is the efficiency of the ramp?

   • A. 60%
   • B. 75%
   • C. 90%
   • D. 30%

More in Energy, Work, Power and Machines

• ▸Forms of Energy & Conservation
• ▸Concept and Measurement of Work
• ▸Power and the Rate of Doing Work
• ▸Introduction to Machines, Mechanical Advantage and Velocity Ratio
• ▸Levers and the Principle of Moments
• ▸Pulleys and Pulley Belt Systems
• ▸Inclined Planes, Wedges and Screws
• ▸Wheel, Gears and Hydraulics

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