A2 kg ball b is travelling horizontally at 10 m/s when it strikes 2 kg ball a. ball a is initially at rest and is attached to a spring with constant 100 n/m and an unstretched length of 1.2 m. knowing the coefficient of restitution between a and b is 0.8 and friction between all surfaces is negligable, determine the normal force between a and the ground when it is at the bottom of the hill.

Total solidification times of three casting geometries are to be compared: a sphere, a cylinder, in which the length-to-diameter ration - 1.0, and a cube. volume = 1000 cm^3 for all three shhapes, and the same casting alloy is used. a) determine the solidification times of each geometry b) based on the results of part (a), which geometric element would make the best riser? c) if the mold constant = 3.5 min/cm^2 in chvorinov's rule, compute the total solidification time for each casting.