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.

Question

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.  
1) What is the acceleration of a .800 gram drop of blood in the fingertips at the bottom of the swing?

i already got the answer its 1.54 m/s^2
 
***i don't know how to solve problems 2 and 3 
 2) Find the force that the blood vessel must exert on the drop of blood in part (a). 
F=? N

3) What force would the blood vessel exert if the arm were not swinging?
F=? N 
 i know the this problem formula is f=ma