Describe how cell membranes are selectively permeable

Cell membranes are selectively permeable because it allows some things to enter or leave the cell while keeping other things outside or inside the cell.

Kinetic energy = 1/2mv^2. since the mass is constant we can form a ratio of it's kinetic energy at 60 divided by that at 30 to see ke(60)/ke(30) = +(60^2)/30^2). this may be said to 300% increase.