Power, velocity and frictional resistance

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SUMMARY

The discussion focuses on calculating the frictional resistance of a car with a mass of 1365 kg and a 60 kW engine, achieving a maximum speed of 145 km/h. The frictional force was determined to be 149205 N using the equation P = F.v. Additionally, the maximum speed of the car on a gradient of 1 in 5 was calculated, but the assertion that friction remains constant at varying speeds was challenged, indicating that friction changes with speed.

PREREQUISITES
  • Understanding of basic physics concepts, particularly forces and motion.
  • Familiarity with the equation P = F.v for power calculations.
  • Knowledge of gravitational force calculations, including mgsinθ.
  • Ability to perform unit conversions, particularly between km/h and m/s.
NEXT STEPS
  • Study the impact of speed on frictional resistance in automotive physics.
  • Learn about the effects of gradients on vehicle performance and speed calculations.
  • Explore advanced power and force equations in physics, particularly in relation to automotive engineering.
  • Investigate the relationship between engine power output and vehicle acceleration.
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Automotive engineers, physics students, and anyone interested in vehicle dynamics and performance calculations.

Darth Frodo
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Homework Statement


(a) A car of mass 1365kg has 60kW engine and a max speed of 145km/hr. Find the frictional resistance.

(b) Calculate max speed of car up a gradient of 1 in 5 if Friction stays the same.

Homework Equations



P = F.v

The Attempt at a Solution



60000 = F (40.2m/s)
F = 149205 N


(b) P = netF . V
60000 = (1492.5 + mgsinθ)
θ = angle of inclination
60000 = [1492.5 + (1365)(9.8)(1/[itex]\sqrt{26}[/itex])]V
v = 60000/4118.6 = 14056 m/s


Is this correct?
 
Physics news on Phys.org
It looks good to me!

The question isn't quite right; friction will not remain the same as the speed changes.
 

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