A 30 kg mass is initially at rest on the floor of a truck. The coefficient of static friction between the mass and the floor of truck is 0.3 and coefficient of kinetic friction is 0.2. Initially the truck is travelling due east at constant speed. Find the magnitude and direction of the friction force acting on the mass, if : (Take g=10 m/s2 )
a. The truck accelerates at 1.8 m/s2 eastward
b. The truck accelerates at 3.8 m/s2 westward.