What is the source of all magnetism?

Gravitational waves

Sound waves

The core of the Earth

Electric current

A 1-lb block and a 100-lb block are placed side by side at the top of a frictionless hill. Each is given a very light tap to begin their race to the bottom of the hill.

For hundreds of years humans have been adding chemicals and other pollutants to the earths water supply. Can earths water ever be clean and pure again? What is clean and pure water?

A 25-foot ladder leans against a wall so that it is 20 feet high at the top. The ladder is moved so that the base of the ladder travels toward the wall twice the distance that the top of the ladder moves up.

Which statement is true about the loudness of sound?

4. Climbing up a tree Charlotte and her lunchbox have a weight of 650 N and she climbs a height of 22 m-how much work does she do in climbing the tree?

Which solid is the best thermal insulator A. brass b. ice C. styrofoam D. copper

When a high-mass star explodes, which of the following is left over in the center? A. Black hole B. Neutron star C. White Dwarf D. either a or b

Which object is an insulator?

Whats the difference between population density and population size?

A standing wave is established in an organ pipe that is closed at one end. What is located at the open and closed ends of the pipe?