Physics Help
posted by GG .
While a person is walking, his arms swing through approximately a 45° angle in .530s. As a reasonable approximation, we can assume that the arm moves with constant speed during each swing. A typical arm is 70.0 cm long, measured from the shoulder joint. (a) What is the acceleration of a .800 gram drop of blood in the fingertips at the bottom of the swing?
1.54m/s^s i got correct
(b) Find the force that the blood vessel must exert on the drop of blood in part a.
im having touble solving this problem and part c
(c) What force would the blood vessel exert if the arm were not swinging?
i know the formula i use is F=ma

I am having trouble with part b myself but for part c the only force is gravity. So F=ma =.0008kg*9.8m/s^2 =0.00784N