Weebly · Web viewA block and tackle is a rope and pulley system that uses multiple pulleys. It...
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10. Energy, Work and Mechanical Efficiency - Mechanical efficiency is a ____________________ of the useful work or energy that a mechanical _____________ produces to the work or energy that was put ___________ the system. - Efficiency is written as a _________________, and can be calculated as follows: mechanical efficiency (%) = _output energy (or work)__ × 100 % input energy (or work) - We want ________________ to have a high level of efficiency so that we _____________ less energy performing everyday tasks. - No machine is 100 % _______________________. - Even simple machines ____________________ small amounts of friction and slippage. - Complex machines are made of __________ simple machines, so the friction and slippage ____________________, making the complex machine less efficient than its __________________ parts. - Energy can be __________ from slippage or friction. Pulleys - Many work sites use pulleys to ___________ objects. - For example, a ____________ has a pulley system. - This pulley system can be used to lift __________ objects to great heights. - A pulley system that is old and ______________ will not be very efficient. (friction) - A new pulley system that moves _____________ is more efficient. Levers - Levers are ________________ quite efficient.
Transcript of Weebly · Web viewA block and tackle is a rope and pulley system that uses multiple pulleys. It...
10. Energy, Work and Mechanical Efficiency- Mechanical efficiency is a ____________________ of the useful work or energy that a mechanical _____________
produces to the work or energy that was put ___________ the system.
- Efficiency is written as a _________________, and can be calculated as follows:
mechanical efficiency (%) = _output energy (or work)__ × 100 % input energy (or work)
- We want ________________ to have a high level of efficiency so that we _____________ less energy performing everyday tasks.
- No machine is 100 % _______________________.
- Even simple machines ____________________ small amounts of friction and slippage.
- Complex machines are made of __________ simple machines, so the
friction and slippage ____________________, making the complex
machine less efficient than its __________________ parts.
- Energy can be __________ from slippage or friction.
Pulleys
- Many work sites use pulleys to ___________ objects.
- For example, a ____________ has a pulley system.
- This pulley system can be used to lift __________ objects to great heights.
- A pulley system that is old and ______________ will not be very efficient. (friction)
- A new pulley system that moves _____________ is more efficient.
Levers
- Levers are ________________ quite efficient.
- When the bar is _____________ and the ________________ is hard and slightly pointed or rounded, there is minimal friction and
____________ energy is lost.
- However, sometimes even simple machines are
___________________.
CHECK YOUR LEARNING
1. Use a Venn diagram to compare the everyday meaning of efficiency from Section 3.2 and its scientific meaning from this section.
2. How efficient is a pulley system if an
operator has to pull 4.0 m of rope to raise a 250 N pail of water a distance of 2.0 m? The operator is pulling with a force of 150 N.
3. A block and tackle is a rope and pulley system that uses multiple pulleys. It multiplies a small force into a large one. If a motor has a weight of about 2500 N and people pull 4.0 m of rope with a force of 700 N to raise the motor 1.0 m, how efficient is the block and tackle?
4. Name something you can do to increase the efficiency of your bicycle.
