Một tường lò xây bằng hai lớp lớp rạch samot dày §=120mm hệ số dẫn nhiệt là ¥=0.93w/m. k và lớp rạch đỏ dày §=250mm hệ số dẫn nhiệt ¥=0.7w/m. k Nếu thêm vao giữa một lop bột diatomit dày 50mm, ¥=0.113+0.00023t w/m. K thì chiều dày lớp gạch đỏ sẽ bằng bao nhiêu để mật độ dòng điện qua tường không thay đổi. Biết nhiệt độ mặt trong và ngoài cua tường bằng 1000°c và 50°c

Answerwavelength;

The boat's velocity relative to the riverbank can be resolved into two components. the component going north is 2.7 m/s and the component going west is 1.2 m/s.we add these two vectors and then find the magnitude of the resultant to get the speed.the magnitude of the resultant vector from adding can be obtained by the pythagorean theorem.    to two significant figures, the boat's speed relative to the riverbank is 3.0 m/s.

Ai think hope that

Distance covered = speed x timethe distance traveled going against the stream = distance traveled with the stream.therefore it is the speed and the time that are the variables.as he travels the same distance both ways, speed x time is the same for each way.going upstream his speed is 4 kph; going downstream his speed is 6 kph.therefore we have two simultaneous equations: time upstream x 4 = time downstream x 6time upstream + time downstream = 60 minutestherefore we have the equation: time upstream = 6/10 hour, time downstream therefore = 4/10 hour.distance traveled at 4km/hr in 6/10 hour = 24/10 = 2.4km.check: distance traveled at 6km/hr in 4/10 hour = 24/10 = 2.4km.