6. a particle of mass is released from the position a of a semi-sphere and moves frictionless on its inner surface as shown in the figure. i) plot the force - cos diagram. ii) calculate the magnitude of the velocity ⃗ of the particle at the position a so that the magnitude of the force exerted on the particle at the position c to be = 4. 7. two perpendicular planes one made up from wood and the other from plastic are in contact as shown in the figure. the depth of each plane is = 5 . the projectile a passes through the wooden plane and stops inside the plastic plane at a distance of 1= 2 . the projectile c passes through the plastic plane and stops inside the wooden one at a distance of 2 = 1 . if the resistance forces on the projectiles from the wood and plastic are assumed constant during the motion of the projectiles, calculate the ratio ⁄.