Activity 1.2.5 Mechanical System Efficiency ATV
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|Activity 1.2.5 Mechanical System Efficiency |
Introduction
|Energy cannot be created or destroyed, but energy can be converted from one form to another. By |[pic] |
|design, an engineer creates an energy conversion system to change an input energy form into a | |
|desired output energy form. However, within a conversion system, input energy can be changed into|[pic] |
|less desirable forms of energy. Less desirable forms of energy conversion can occur due to | |
|resistance and friction, resulting in thermo energy conversion. Engineers strive to decrease |[pic] |
|undesirable energy conversions within a system, or energy losses, by planning with system | |
|efficiency in mind. Efficiency is the ratio of desired output energy compared to input energy. | |
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|A common form of energy conversion today occurs through electromagnetic induction. | |
|Electromagnetic induction transfers mechanical energy into electrical energy. The electrical | |
|energy is then transmitted to industries and homes to be used in a variety of ways, many of which| |
|include conversion back to mechanical energy. | |
Equipment
• Calculator
Procedure
In this activity you will investigate an energy conversion system designed to change electrical energy into mechanical energy. Given ATV (All-Terrain Vehicle) winch data, you will determine the efficiency of the system under various loads. Remember units and precision when recording data.
ATV Winch Data
ATV winches pull a horizontal load during testing. The winch pulls a weight where the friction produces a force which is measured as tension in the cable. The following data can be used to compare electrical input to mechanical output to determine system efficiency.
|Force |Distance |Time |Current |Volts |
|0 |24 m |180 s |15 A |12 V |
|7000 N |24 m |360 s |100 A |12 V |
|11000 N |24 m |720 s |160 A |12 V |
Work involves the amount of force (F) exerted over a specific distance (d). Note that work is not related to time. For example running up a flight of stairs in four seconds requires a different level of exertion than if you walk up a flight of stairs in thirty seconds. You will feel differently in each scenario even though you did the same amount of work. Use the following formula to determine how many joules (J) of work it took to lift the weight in the system. As you carry your units through to the solution, change the final answer from N∙m to J.
1. Determine the work done by the winch system for each test.
|Formula |Substitute / Solve |Final Answer (0) |
|W = F∙d | |0J |
| | | |
| |0*24=0 | |
| | |168000J |
| |7000*24 | |
| | | |
| | |264000J |
| | | |
| |11000*24 | |
Power involves time, force, and distance. In the previous example, the same amount of work was done regardless of time. To climb the stairs more quickly, a person needs more power. Use the formula below to calculate the output power of the system in watts (W). As you carry your units through to the solution, change the final answer from J/s to W.
1. Determine the output power of the system for each test. Your final answer will be in watts.
|Formula |Substitute / Solve |Final Answer (0.0) |
|[pic] |0J/180 |0W |
| |168000J/360 |466.66W |
| |264000J/720 |366.66W |
2. To calculate power of an electrical system, multiply the current and voltage. Substitute and solve to discover how many watts were put into your system. You do not need to show the relationship of units to solve the problem, but be sure to label your final answer as watts.
|Formula |Substitute / Solve |Final Answer(0) |
| |15*12 |180W |
|[pic]Pin = IV | | |
| |100*12 |1200W |
| |160*12 |1920W |
3. In order to compare the energy input versus the output, the efficiency of the system must be determined. Use the given formula to calculate efficiency.
|Formula |Substitute / Solve |Final Answer (0.0) |
|[pic] |0*180]*100 |0% |
| |[466.66/1200]*100 |38.88% |
| |[366.66/1920]*100 |19.09% |
Conclusion
1. Which scenario is most efficient? What factors make one scenario more efficient than another?
The second scenario. The input power was less in comparison to the output than the other ones.
2. List and describe three factors that reduce the efficiency of this winch system.
Friction with the ground, friction in the winch, and the ratio of input to output power
1. Describe at least one strategy for making this system more efficient.
Gear ratio to the motor to increase torque, allowing for less input power
2. Explain at least two reasons why automotive engineers are concerned with improving vehicle efficiency.
Better MPG’s can help to sell the car because consumers don’t want to pay lots for gas.
If the efficiency is not good enough, the friction can generate heat, making it less efficient.
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