A 30-N iPad is dropped from a height of 10 m and strikes the ground with a speed of 13 m/s. What average force of air friction acted on the iPad as it fell?​

Two red blood cells each have a mass of 9.0 multiply.gif 10-14 kg and carry a negative charge spread uniformly over their surfaces. the repulsion arising from the excess charge prevents the cells from clumping together. one cell carries −2.50 pc of charge and the other −3.10 pc, and each cell can be modeled as a sphere 7.5 μm in diameter. (a) what speed would they need when very far away from each other to get close enough to just touch? assume that there is no viscous drag from any of the surrounding liquid. answer is: 321 m/s how do i find this (b) what is the maximum acceleration of the cells in part (a)? answer is: 1.38e+10 m/s2 how did they find this answer

When you push downward on a book at rest on a table, you feel an upward force. does this force depend on friction? defend your answer.

If you put a helium-filled balloon in the refrigerator, what will happen?