Hai điện tích điểm bằng nhau đặt trong điện môi lỏng ε = 81 cách nhau 3 (cm) chúng đẩy nhau bởi lực 2 (μN). Độ lớn các điện tích là

The radiation of the fire causes the saucepan to heat up. the conduction of the saucepan then to distribute the heat over the saucepan and to give heat to the water. the convection of the water distributing the heat within the water, till all the water is boiling

  concave means having an outline or surface that curves inward like the interior of a circle or sphere. so the mirror curves inward.

The answer is  the potential energy of the bob at position b is 1.47 joules.if the maximum height of the bob is 0.45 meters when it swings back,1.323   joules of energy was transformed to thermal energy.hope this