(30 pts.) According to the Darcy-Weisbach equation, the loss in power-generating capacity (P) in a hydroelectric system due to head loss (H) is: P QH =ηγ where η is turbine efficiency, γ the specific gravity of water, Q the volumetric flow rate, and H the head loss. Measurements over a particular stretch of time yielded the summary data below: Parameter Mean value Standard deviation η 0.85 0.02 γ 9800 N/m3 0.0 N/m3 Q 60 m3 /s 1.00 m3 /s H 3.71 m 0.10 m a) What is the uncertainty (variance) in P that can be attributed to variations in the above measurements? b) Which of the following actions would provide the greatest reduction in uncertainty in P: a) reduce uncertainty in η to 0.01, reduce uncertainty in Q to 0.5, or reduce uncertainty in H to 0.05?

A3.9 g aluminum foil ball with a charge of +4.1×10−9 c is suspended on a string in a uniform horizontal e⃗ field. the string deviates to the right and makes an angle of 30∘ with the vertical. part a part complete what information about the e⃗ field can you determine for this situation? what information about the field can you determine for this situation? only the magnitude of e⃗ only the direction of e⃗ both the magnitude and the direction of e⃗ none of the above previous answers correct part b determine the magnitude of the electric field. express your answer with the appropriate units. e e = nothing nothing request answer part c determine the direction of the electric field. determine the direction of the electric field. to the right to the left away from you toward you

Imagine that someone pushes one marble toward a motionless marble. would there still be action-reaction forces involved in the collision? how might the marbles’ motions be changed? ?

Imagine you are standing in the antarctic during the southern hemisphere summer. the sky is clear and blue. there are no clouds in the sky. your shadow is cast on the icy ground. what is the color of the shadow?