Hai hạt bụi trong không khí cách nhau 3cm mỗi hạt mang điện tích -9,6.10 mũ -13C. A )Tính lực đẩy tĩnh điện giữa hai hạt B ) tính số electrong dư trong mỗi hạt bụi biết diện tích củ mỗi electrong -1,6.10 mũ -19C

Blank liquids and gases exert a buoyant force on objects placed in them

As you are trying to move a heavy box of mass m, you realize that it is too heavy for you to lift by yourself. there is no one around to , so you attach an ideal pulley to the box and a massless rope to the ceiling, which you wrap around the pulley. you pull up on the rope to lift the box. use g for the magnitude of the acceleration due to gravity and neglect friction forces. once you have pulled hard enough to start the box moving upward, what is the magnitude f of the upward force you must apply to the rope to start raising the box with constant velocity? express the magnitude of the force in terms of m, the mass of the box.

Estimate the schwarzschild radius (in kilometers) for a mini-black hole formed when a superadvanced civilization decides to punish you (unfairly) by squeezing you until you become so small that you disappear inside your own event horizon. (assume that the your weight is 50 kg)