Why Should the Power Output Be 47.7 Horsepowers?

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SUMMARY

The power output required for a 2400-pound car ascending a 10-degree slope at 30 miles per hour is 47.7 horsepower, accounting for a 70% efficiency rate. The formula used is Power = (force)(velocity), where 1 horsepower equals 550 ft*lb/s. The calculated power output at 70% efficiency is 23.38 horsepower, but this represents only the useful power, not the total engine power needed. To achieve the necessary power output, one must consider that the engine must produce more than the useful power due to efficiency losses.

PREREQUISITES
  • Understanding of basic physics principles, particularly force and motion.
  • Familiarity with power calculations, specifically the relationship between horsepower and foot-pounds per second.
  • Knowledge of efficiency concepts in mechanical systems.
  • Ability to apply trigonometric functions to resolve forces on inclined planes.
NEXT STEPS
  • Study the calculations for power output in inclined planes using the formula Power = (force)(velocity).
  • Research the implications of efficiency in engine performance and how it affects power requirements.
  • Learn about the conversion between horsepower and other power units, such as watts.
  • Explore real-world applications of power calculations in automotive engineering.
USEFUL FOR

Automotive engineers, physics students, and anyone involved in vehicle performance analysis will benefit from this discussion.

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A 2400 pound car ascends a 10 degree slope at 30 miles per hour. If the overall efficiency is 70 percent, the power output at 70 percent efficiency is 47.7 horsepowers.

By the formula, Power=(force)(velocity) with 1 horsepower=550 ft*lb/s , the power output at 70% efficiency is 23.38 horsepowers.

Can someone explain why it should be 47.7 horsepowers?
 
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Power = (force)(velocity) will give you the power you need to move the car. You have to find the engine power that will produce the needed power considering that only 70% is useful power. (You took 70% of the power you need, not 70% of the engine power.)
 

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