What element has 81 protons in the nuclei of atoms

"an open tank has the shape of a right circular cone. the tank is 6 feet across the top and 5 feet high. how much work is done in emptying the tank by pumping the water over the top edge? note: the density of water is 62.4 lbs per cubic foot."

According to newton’s first law of motion, which force is expected to cause a body to accelerate?

A2k pendulum has a speed of 1 m/s at a height of 1/2 meter