a) a student eats a breakfast consisting of two bowls of cereal and milk, contai

Question

a) a student eats a breakfast consisting of two bowls of cereal and milk, containing a total of 3.10 x 10^2 Calories of energy. He wishes to do an equivalent amount of work in the gym by doing curls with a 24.0 kg barbell. How many times must he raise the weight to expend that much energy. Assume that he raises it through a vertical displacement of .400 m each time, the distance from his lap to his upper chest.


b) How many sprints from rest to a speed of 5.2m/s would a 56 kg woman have to complete in order to burn off 5.0 x 10^2?(Assume 100% efficiency in converting food energy to mechinical energy. Ignore the energy expenditure of slowing down.)

Explanation / Answer

As its is against to the rules of the website to ost multiple questions in asingle post, I am going to answer one of the above questions. REMEMBER THAT FURTHER MULTIPLE POSTS WILL NOT BE ENTERTAINED.

 

a)

 

The total energy of the breakfast is E = 3.10*10^2 cal = 1298.90 J

 

The mass of the barbell is m = 24 kg

 

The height through which the barbell is raised is h = 0.4 m

 

The energy required to raise the barbell through the given height for one time is

 

= mgh

 

= 24*9.8*0.4

 

= 94.08 J

 

Let n be the number of times required to raise the weight to expend that much energy

 

E = n

 

n = E/

 

n = 1298.90/94.08

 

n = 13.806

 

n = 14 times  (appx)

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