A strong magnetic field surrounds Earth. How does Earth’s magnetic field help humans? It holds people’s belongings tight to Earth’s surface.
It’s responsible for cycling water through Earth’s four spheres.
It keeps the solar wind from reaching Earth.
It helps people navigate using a compass.
It helps cool Earth’s surface.

Your physics assignment is to figure out a way to use electricity to launch a small 6.0-cm-long plastic drink stirrer. you decide that you'll charge the little plastic rod by rubbing it with fur, then hold it near a long, charged wire, as shown in figure p23.56 . when you let go, the electric force of the wire on the plastic rod will shoot it away. suppose you can uniformly charge the plastic stirrer to 10 nc and that the linear charge density of the long wire is 1.0 x10-7 c/m. what is the net electric force on the plastic stirrer if the end closest to the wire is 2.0 cm away?