# Calculating Energy Changes in a Crane Lifting a Beam: A Scientific Analysis

• Alaa Wahbi
In summary, the crane's engine transferred 4.0×10000 J of energy to the air, which transferred 1 MJ of energy to the crane, which raised the beam 1000 kg with no change in total energy.
Alaa Wahbi

Hi every one,

i'm gettin crazy trying to solve this question, please do help if u could, i would really appreciate that.

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** A crane uses its petrol engine to lift a beam of mass 1000 kg by height h. The fuel burned loses 1 MJ (million J) of chemical potential energy, 85% of this being transferred by heating to the air. The internal energy of the crane's engine increases by 4.0×10000 J, while that of the crane's superstructure and the beam is unchanged. The crane's superstructure ( not engine of fuel) increases in graviational potential energy by 10000 J. Everything is at rest before and after. Assume all transfer by working out of the crane is used to lift the beam.

(a) The calorific value of the fuel is 43 MJ/kg, its density is 737 kg m(to power -3) and it costs 90p (pens) per liter (there are 1000 liter in 1 m to power 3). What was the fuel cost of raising the beam?
(b) What is the change in total energy of the beam in terms of h?
(c) Consider the energy changes of the whole crane (fuel + engine + superstructure) to find the height h.
(d) Consider the energy changes of the engine (including fuel). If the whole process takes 55 seconds, find the average power output by working of the engine.

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Welcome to the PF. As per the guidelines that you just agreed to, you must show your own work so far in order for us to help you. What kind of energy and work equations have you been using so far on these problems?

Hi berkeman,

thanks for ur replay, however I am really sorry that i couldn't reach any point of myself work. Because i don't understand the question properly, maybe coz the language is a problem for me, I'm not a native speaker!

I need some hints or any thing like that, I would use equations like:

(Delta) E= W + Q

so,

Kinetic Energy + Potential Energy + Internal Energy = W + Q

where W is the work.
Q is the amount of energy transferred by heating.

would these equations be correct ?

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