Three people pull simultaneously on a stubborn donkey. Jack pulls eastward with a force of 83.7 N , 83.7 N, Jill pulls with 73.1 N 73.1 N in the northeast direction, and Jane pulls to the southeast with 181 N . 181 N. (Since the donkey is involved with such uncoordinated people, who can blame it for being stubborn?) Find the magnitude of the net force the people exert on the donkey.

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

Plss anybody know how to do this? ? i need the answers from a through d

How is sound energy produced a. vibrating objects b. objects being heated c. temperature differences d. stationary objects