Why does an iron core increase the magnetic induction of a coil?

Astone is thrown into a pond. what happens to the amplitude of the resulting waves as they get farther from the point where the stone hit the water? explain.

Which articulations allow for greatest range of motion?

Two pans of a balance are 24.1 cm apart. the fulcrum of the balance has been shifted 1.33 cm away from the center by a dishonest shopkeeper. by what percentage is the true weight of the goods being marked up by the shopkeeper? assume the balance has negligible mass. answer in units of %.