Toeboards are usually__ and used on landings and balconies

Ahollow metal sphere has 6 cm and 11 cm inner and outer radii, respectively. the surface charge density on the inside surface is −100nc/m2. the surface charge density on the exterior surface is:

A26 cm object is 18 cm in front of a plane mirror. a ray of light strikes the object and is reflected off the mirror at a 42-degree angle. what is the angle of reflection? degrees what type of image is formed? what is the size of the image? cm

Imagine that someone pushes one marble toward a motionless marble. would there still be action-reaction forces involved in the collision? how might the marbles’ motions be changed? ?