Answer: A) Cm = 2.232 s/mm² B) Time taken to solidify = 74.3 seconds Explanation: (A) Since a side is 50mm and all sides of a cube are equal, thus, Volume of the cube is;V = 50 x 50 x 50 = 125,000 mm³ There are 6 faces of the cube, thus Surface Area A = 6 x (50 x 50) = 15,000 mm² So, Volume/Area = (V/A) = 125,000/15,000 = 8.333 mm Cm is given by the formula; Cm =[Tts] /(V/A)² where Tts is time taken to solidify and it's 155 seconds in the question. Thus; Cm = 155/(8.333)²= 2.232 s/mm² (B) For;Cylindrical casting with D = 30 mm and L = 50 mm.; Volume of cylinder is; V = (πD²L) /4 So,V = (π x 30² x 50)/4 = 35,343mm³ Surface area of cylinder is; A = (2πD²)/4 + (πDL) Thus, A = ((π x 30²)/2) + (π x 30 x 50) = 6126 mm² Volume/Area is; V/A = 35,343/6126 = 5.77 mm Same alloy and mold type was hsed as in a above, thus, Cm is still 2.232 s/mm² Since Cm =[Tts] /(V/A)² Making Tts the subject, we have; Tts =Cm x (V/A)² Tts = 2.232 x (5.77)² = 74.3 seconds
