Trong thí nghiệm ở hình 1. 1, nếu ta thắp một nắm hương để cho khói bay lên ở phía trước đèn pin, ta sẽ nhìn thấy một vệt sáng từ đèn phát ra xuyên qua khói. Giải thích vì sao ? Biết rằng khói gồm các hạt nhỏ li ti bay lơ lửng.

Asheet of steel 1.5 mm thick has nitrogen atmospheres on both sides at 1200oc and is permitted to achieve a steady-state diffusion condition. the diffusion coefficient for nitrogen in steel at this temperature is 6 x 10- 11 m2 /s, and the diffusion flux is found to be 1.2 x 10-7 kg/m2 -s. also, it is known that the concentration of nitrogen in the steel at the high-pressure surface is 4 kg/m3 . how far into the sheet from this high-pressure side will the concentration be 2.0 kg/m3 ? assume a linear concentration profile.

You can watch static electricity in action by rubbing an inflated balloon against your hair. your hair will actually stand on its end! it does this because each hair becomes charged, and they all repel one another.

The pilot of a helicopter hovers at an altitude of 1200 feet over a park. the angle of depression to the base of a statue is 17 degrees. the angle of depression to the nearest park exit, in line with the statue, is 14 degrees. to the nearest foot, what is the distance from the statue to the exit?