Power, mass, speed, time and height

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SUMMARY

The discussion revolves around calculating the average power required for a child with a mass of 30 kg to run up a flight of stairs that is 3 meters high in 6 seconds, reaching a speed of 2 m/s at the top. The average power can be determined using the work-energy principle, focusing on the vertical displacement rather than horizontal distance. The key formula involves calculating the work done against gravity, which is the product of mass, gravitational acceleration, and height, divided by time.

PREREQUISITES
  • Understanding of basic physics concepts such as work, energy, and power.
  • Familiarity with the work-energy principle in mechanics.
  • Knowledge of gravitational acceleration (approximately 9.81 m/s²).
  • Ability to manipulate equations involving mass, height, and time.
NEXT STEPS
  • Calculate work done using the formula: Work = mass x gravity x height.
  • Learn how to derive average power from work done over time.
  • Explore the relationship between force, velocity, and power in physics.
  • Investigate uniform acceleration and its implications in motion problems.
USEFUL FOR

This discussion is beneficial for physics students, educators, and anyone interested in understanding the concepts of power and energy in mechanics, particularly in relation to motion and work done against gravity.

furor celtica
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Homework Statement


A child of mass 30 kg runs up a flight of stairs in 6 seconds. The top of the flight is 3 metres above the bottom, and at the top he is running at 2ms^-1. What average power does he need to produce?



The Attempt at a Solution



This is one of the first exercises I have had to tackle concerning power, so I'm pretty sure its meant to be simple. However, in terms of power both force x velocity and work/time i have no idea where to start.

Without the child's starting speed, horizontal distance covered or total distance run I'm at a loss for what to use and what to look for...any suggestions would help.

Homework Equations

 
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The problem is vague about the child's initial speed. I assume since it gives the velocity at the top of the stairs and it talks about average power, that the child starts from rest and accelerates uniformly to reach her given speed at the top.

Buy you don't need horizontal or total distance to find work...you just need the vertical displacement...think about the work- energy equations.
 

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