To work off a large pepperoni pizza you ate on Friday night, on Saturday morning

Question

To work off a large pepperoni pizza you ate on Friday night, on Saturday morning you climb a 115 m high hill (a) Assuming a reasonable value for your mass (say, 75 kg), determine your increase in gravitational potential energy 84.5 kJ (b) Where does this energy come from? The kinetic energy that you use to climb the hill is converted into gpe Score: 0.12 out of 0.12 Comment: (c) The human body is typically 20 percent efficient. How much energy was converted into thermal energy? 67.6 (d) How much chemical energy is expended by you during the climb? 16.9 (e) Given that oxidation (burning) of a single slice of pepperoni pizza releases about 1.0 MJ (250 food calories) of energy, do you think one climb up the hill is enough? Yes No The work you did equals the change in your gravitational potential energy and is enabled by the transformation of metabolic energy in your muscles. Let the system consist of you and Earth and apply the conservation of mechanical energy to this system. eBook

Explanation / Answer

(A) Increase in PE = m g h

= 75 x 9.8 x 115

= 84525 J OR 84.5 kJ  

(B) Ihis energy comes from work done by the body.

from chemical energy of body.

(C) 20% effiencet means energy generate by is E then only 20% of it converts into Work done.

so 0.20 E = 84.5

E = 422.6 kJ  

thermal energy = 422.6 - 84.5 = 338 kJ

(D) chemical energy = E = 422.6 kJ

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