The force of gravity is an inverse square law. this means that, if you double the distance between two large masses, the gravitational force between them

the first american roller coaster was the mauch chunk switchback railway, built in the mountains of pennsylvania in the mid-1800s. the track, originally built to send coal to a railway, was reconfigured as a "scenic tour."

wire in brush may conduct electricity from cell to drill and vice versa electrc shock possible