A 5g bullet moving at 600m/s penetrates a tree trunk to a depth of 4cm.(a)Use the work energy theorem, to determine the average frictional force that stops the bullet.(b)Assuming that the frictional force is constant, determine how much time elapses between the moment the bullet enters the tree and the moment it stops moving.

Cells in the nervous system have a potential difference of 70 mv across the cell membrane separating the interior of the cell from the extracellular fluid. this potential difference is maintained by ion pumps that move charged ions across the membrane. is this an emf? select the correct answer and explanation. 1)no. the ion pumps cannot separate charges; thus, they cannot create a potential difference. 2)yes. the ion pumps cannot separate charges, but they still can create a potential difference. 3)yes. the ion pumps can actively separate charge; thus, they can create a potential difference. 4)no. the ion pumps can separate charges, but they cannot create a potential difference.