Why isn’t the level of water in aquifer always the same?

Debbie places two shopping carts in a cart corral she pushes the first cart which then pushes a second cart what force is being exerted

Where should a carbon monoxide detector be mounted?

The two most prominent wavelengths in the light emitted by a hydrogen discharge lamp are 656(red) and 486 (blue). light from a hydrogen lamp illuminates a diffraction grating with 500 lines per mm, and the light is observed on a screen 1.50 behind the grating. what is the distance between the first-order red and blue fringes?