You leave a 120 W light bulb on for 12 hours in the day (8%) Problem 10: You lea

Question

You leave a 120 W light bulb on for 12 hours in the day

(8%) Problem 10: You leave a 120 W light bulb on for 12 hours in the day " 2596 Part (a) Express energy through power P and time interval dt. 2596 Part (b) How much energy has been used in Joules? 38 2596 Part (c) If the energy used were used to lift a weight ofm 180 kg, write an equation of the height h that the weight can be lifted in terms of P, dt, and m? Grade Summary Potential 100% Attempts remaining: 14 é per attempt) 0% END 0% 0% Submit Feedback: 0% deduction per feedback. Hines:-2 for a deduction Hints remaining: When the we ht is lifted, how does the gravitational potential What energy is the wasted energy transferred to in lifting the energy change

Explanation / Answer

Solution (c):

Let us go to the basics first.

Energy consumed by bulb = P*t   [where P = power; t = time]

Energy required to lift a mass m = mgh   [where g = acceleration due to gravity = 9.8 m/s2]

Equating above two equations, we have:

P*t = mgh  

=>h = (P*t) / (mg) or h = (P*t) / (9.8m)   [Equation of height h è Answer c]

In terms of numerical value:

h = (120*43200) / 1764     [P = 120 W; t = 12 hours = 43200 s; mg = 180*9.8 = 1764 N]  

h = 2938.77 m (Answer)

Thanks!!!

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