Cho điện tích của 1 electron: e=-1,6×10^(-19) C; khối lượng của electron: m_e=9,1×10^(-31) kg; khối lượng của proton: m_p=1,67×10^(-27) kg; hằng số hấp dẫn G=6,67×10^(-11) Nm2/kg2; Bài 1: Cho biết bán kính nguyên tử hydro r=0,53×10^(-10)¬ m.
a) Tính lực hút tĩnh điện và lực hấp dẫn giữa hạt nhân và electron trong nguyên tử hydro.
b) Xác định vận tốc chuyển động của electron trên quỹ đạo bán kính r khi xem lực hút tĩnh điện đóng vai trò là lực hướng tâm.

We want to calculate the total metabolic heat generated by a singing canary taking into account heat transfer by radiation, convection and exhaling air. the air temperature is 20 oc, canary’s body internal and surface temperature is 33oc, external body surface convective heat transfer coefficient is 25.2 w/m2 .k, temperature difference between the inhaled and exhaled air is 4.3 oc, the ventilation rate is 0.74 cc of air per second, specific heat of air is 1.0066 kj/kg.k and density of air is 1.16 kg/m3 . assume the canary’s body to be a cylinder with 7 cm diameter and 9 cm length, and heat exchange is from the side as well as the top and bottom of cylinder. calculate 1) the net rate of heat lost by radiation, assuming heat gained by the bird through radiation from the surroundings is 11.5 w; 2) rate of heat transferred by convection to the surrounding air; 3) rate of heat transferred in the exhaling air without considering any internal evaporation; 4) total metabolic power.

What is the single most important equation in all of physics?

A15,000 kg rocket traveling at +230 m/s turns on its engines. over a 6.0 s period it burns 1,000 kg of fuel. an observer on the ground measures the velocity of the expelled gases to be −1,200 m/s.