Work, Energy & Power: Solving 20 & 21 Problems

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SUMMARY

The discussion focuses on solving physics problems related to work, energy, and power, specifically problems 20 and 21 from a homework assignment. For problem 20, a 22 kW car engine can perform 1320 kJ of work in 60 seconds, calculated using the formula Work = Power x Time. In problem 21, the work done by a 5.0 N force moving a 6.0 kg object at a constant speed of 2.5 m/s over 25 seconds is 125 J, with a power output of 5 W. The force of friction acting on the object is equal to the applied force of 5.0 N, as the object moves at constant speed.

PREREQUISITES
  • Understanding of basic physics concepts such as work, energy, and power.
  • Familiarity with the formulas W = F * d and P = E/t.
  • Knowledge of units of measurement for power (kW) and work (Joules).
  • Ability to perform calculations involving time and force in physics problems.
NEXT STEPS
  • Study the principles of energy conservation in mechanical systems.
  • Learn about the relationship between force, mass, and acceleration in Newtonian physics.
  • Explore the concept of efficiency in engines and mechanical systems.
  • Investigate frictional forces and their impact on motion in physics.
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone looking to deepen their understanding of work, energy, and power calculations in mechanical contexts.

McKeavey
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Homework Statement


20. How much work can a 22kW car engine do in 60s if it is 100% efficient?

21. A force of 5.0N moves a 6.0 kg object along a rough floor at a constant speed of 2.5m/s.
a) How much work is done in 25s?
b) What power is being used?
c) What force of friction is acting on the object?



Homework Equations





The Attempt at a Solution


I would guess that I need to use W = F * d , but got nowhere.

W = F * d
P = E/t
got nowhere too..
 
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Work= Power x time. so much work would the car do, since P =22 kW and t=60 s ?

since its 100 % efficient, all the energy given by the engine is used for moving the car
 

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