A hot surface at 150°C is to be cooled by attaching 30 mm-long
aluminum pin fins (k= 237 W/m·K) having
the square cross-section (3-mm x 3-mm) as
shown in figure. The temperature of the
surrounding medium is 25°C, and the heat
transfer coefficient on the surfaces is 30
W/m2
·K. Determine the rate of heat transfer
from the surface for a 57-mm x 53-mm
section of the plate. Also determine the
overall effectiveness of the fins

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

Consider a double atwood machine constructed as follows: a mass 4m is suspended from a string that passes over a massless pulley on frictionless bearings. the other end of this string supports a second similar pulley, over which passes a second string supporting a mass of 3m at one end and m at the other. using two suitable generalized coordinates, set up the lagrangian and use the lagrange equations to find the acceleration of the mass 4m when the system is released. explain why the top pulley rotates even though it carries equal weights on each side.

Contains chemical energy. a. heat b. light c. natural gas