Why is it useful to create neptunium by bombarding uranium with protons, even though neptunium disintegrates in about two days?

Molten iron fills a mould, which has a volume of 200 cm cubed. calculate the volume when the iron cools and solidifies.

Two forces produce equal torques on a door about the door hinge. the first force is applied at the midpoint of the door; the second force is applied at the doorknob. both forces are applied perpendicular to the door. which force has a greater magnitude?

By what factor does the drag force on a car increase as it goes from 65 to 110 km/h?