hai dòng điện có cường độ I1=2A, I2=4A. chạy trong hai dây dẫn thẳng dài vô hạn, đồng phẳng , vuông góc với nhau trong không khí . trong mặt phẳng có hai dòng điện , quỹ tích tại đó véc tơ tại đó cảm ứng từ bằng 0 là đường thẳng nào ?

Astudent is given an assignment to demonstrate diffraction. he takes a photograph of a straw in a glass of water. the straw appears bent at the water level. which best describes this example? a) this is a good example of diffraction. b) this is an example of dispersion and not diffraction. c) this is an example of refraction and not diffraction. d) this is an example of reflection and not diffraction.

What effects result when there is an impact between earth and an asteroid? check all that apply. a. massive flooding. b. extinction of many life forms. c.major earthquakes change in average global temperature. d. giant dust cloud

To place a communications satellite into a geosynchronous orbit at an altitude of 22,240 mi above the surface of the earth, the satellite first is released from a space shuttle , which is in a circular orbit at an altitude of 185 mi, and then is propelled by an upper-stage booster to its final altitude. as the satellite passes through a, the booster's motor is fired to insert the satellite into an elliptic transfer orbit. the booster is again fired at b to insert the satellite into a geosynchronous orbit. knowing that the second firing increases the speed of the satellite by 4810ft/s, determine (a.) the speed of the satellite as it approaches b on the elliptic transfer orbit, (b.) the increase in speed resulting from the first firing at a.