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 Energy and Work Energy and Work Physics Help Forum

 Dec 19th 2009, 08:02 PM #1 Junior Member   Join Date: Dec 2009 Posts: 2 I need help! 1. Explain how the scientific definition of work is different from the everyday meaning. 2. Describe a situation in which a force is applied, but no work is done. 3. Calculate Work A car's engine produces 100 kW of power. How much work does the engine do in 5 s? 4. Describe the circumstances for which the output work would equal the input work in a machine. 5. Infer how lubricating a machine affects the output force exerted by the machine. 6. Explain why in a real machine the output work is always less than the input work. 7. Think Critically The mechanical advantage of a machine is less than one. Compare the distances over which the input and output forces are applied. 8. Calculate Efficiency Find the force needed to lift a 2,000-N weight using a machine with a mechanical advantage of 15. 9. Classify a screwdriver as one of the six types of simple machine. Explain how the IMA of screw driver could be increased. 10. Determine for which class of lever the output force is always greater then the input force. For which class is the output force always less than the input force? 11. Make a diagram of a bicycle and label the the parts of a bicycle that are simple machines. 12. Think Critically Use the law of conservation of energy to explain why in a second-class lever the distance over which the input force is applied is always greater than the distance over which the output force is applied. 13. Calculate Output Arm Length A lever has an IMA of 4. If the length of the input arm is 1.0 m, what is the length of the output arm? 14. Determine which of the levers listed in the table above has the largest IMA. 15. Describe how the effort force, resistance force and fulcrum should be arranged so that a child can lift an adult using his own body weight on a see saw. 16. Explain which would give the best mechanical advantage for driving a screw down into a board: a screwdriver with a long, thin handle, or a screwdriver with a short fat handle. 17. Calculate Axle Radius A doorknob has an IMA equal to 8.5. If the diameter of the doorknob is 8.0 cm, what is the radius of the shaft the doorknob is connected to? 18. Calculate Efficiency Using a ramp 6 m long, workers apply an input force of 1,250 N to move a 2,000-N crate onto a platform 2 m high. What is the efficiency of the ramp? Thanks! Last edited by ChaunaLynn; Dec 19th 2009 at 08:04 PM. Reason: i forgot one!
Dec 19th 2009, 08:27 PM   #2
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 Originally Posted by ChaunaLynn 1. Explain how the scientific definition of work is different from the everyday meaning. 2. Describe a situation in which a force is applied, but no work is done. 3. Calculate Work A car's engine produces 100 kW of power. How much work does the engine do in 5 s? 4. Describe the circumstances for which the output work would equal the input work in a machine. 5. Infer how lubricating a machine affects the output force exerted by the machine. 6. Explain why in a real machine the output work is always less than the input work. 7. Think Critically The mechanical advantage of a machine is less than one. Compare the distances over which the input and output forces are applied. 8. Calculate Efficiency Find the force needed to lift a 2,000-N weight using a machine with a mechanical advantage of 15. 9. Classify a screwdriver as one of the six types of simple machine. Explain how the IMA of screw driver could be increased. 10. Determine for which class of lever the output force is always greater then the input force. For which class is the output force always less than the input force? 11. Make a diagram of a bicycle and label the the parts of a bicycle that are simple machines. 12. Think Critically Use the law of conservation of energy to explain why in a second-class lever the distance over which the input force is applied is always greater than the distance over which the output force is applied. 13. Calculate Output Arm Length A lever has an IMA of 4. If the length of the input arm is 1.0 m, what is the length of the output arm? 14. Determine which of the levers listed in the table above has the largest IMA. 15. Describe how the effort force, resistance force and fulcrum should be arranged so that a child can lift an adult using his own body weight on a see saw. 16. Explain which would give the best mechanical advantage for driving a screw down into a board: a screwdriver with a long, thin handle, or a screwdriver with a short fat handle. 17. Calculate Axle Radius A doorknob has an IMA equal to 8.5. If the diameter of the doorknob is 8.0 cm, what is the radius of the shaft the doorknob is connected to? 18. Calculate Efficiency Using a ramp 6 m long, workers apply an input force of 1,250 N to move a 2,000-N crate onto a platform 2 m high. What is the efficiency of the ramp? Thanks!
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 Dec 22nd 2009, 06:11 PM #3 Junior Member   Join Date: Dec 2009 Posts: 2 Thanks! I don't understand these questions. There were 100 questions and out of those 100 questions 18 of them i didn't understand so that's why I'm posting this. I'm not asking for the answers I just want help and for someone to show me. That's all.