Chapter 7: Homework 2 Question 9 of 10 View Policies < > Current Attempt in Progress f 23 -/15 Question 10 of 10 < > -/5 A rock with mass m is thrown upward with initial speed u,. The speed is low enough that air resistance is negligible. When the rock has risen a height h above its initial position its upward speed has decreased to us. Assume that g, m, v, and h are all known, and the goal is to calculate us. During 4 hours one winter afternoon, when the outside temperature was 10C, a house heated by electricity was kept at 21C with the expenditure of 50 kwh (kilowatt-hours) of electric energy. Part 1 Choose the rock as the system. Which of the following equations correctly represents the Energy Principle in the form E, E, + W, for this choice of system? This is not a question about which equation or equations will give the correct answer for us, but which of these equations correctly corresponds to placing the final energy of the system to the left of the equals sign, the initial energy to the right of the equals sign, and the work done on the system to the right of the equals sign. mv+(-mgh) = mv Part 1 (a) What was the average energy leakage in joules per second (watts) through the walls of the house to the environment (the outside air and ground)? 1 Omv + (mgh) = mv +(-mgh) 2' m = mu+(-mgh) Omv-mv = (-mgh) Save for Later watts Save for Later Attempts: 0 of 4 used Submit Answer Part 2 Attempts: 0 of 4 used Submit Answer Part 2 (b) The rate at which energy is transferred between two systems due to a temperature difference is often proportional to their temperature difference. Assuming this to hold in this case, if the house temperature had been kept at 24C (75.2F), how many kwh of electricity would have been consumed? i eTextbook and Media kwh Next choose the system to be the Earth plus the rock. For this choice of system, which of the following equations correctly represents the Energy Principle in the form EE + W? Again, this is not a question about which equation or equations will give the correct answer for us, but which of these equations correctly corresponds to placing the final energy of the system to the left of the equals sign, the initial energy to the right of the equals sign, and the work done on the system to the right of the equals sign. Omv + (mgh) = mu 2' 02mu3+ (-mgh)= ? 1 - 2 = (-mgh) 1 Save for Later 10:37 AM Tue Nov 21 Attempts: 0 of 4 used Submit Answer SUPPORT 96% mv + (mgh) = m + (-mgh) = mu+(-mgh) eTextbook and Media SUPPORT