4. A He atom is approximately 140 pm and weighs 6.6x1024g. If the He-atom is travelling at a speed of 1000 m/s, do I need quantum mechanics to describe the motion? 5. A baseball, weighing 500 g is travelling at 144 km/hr +0.001 km/hr. A baseball is 3.65 cm. Do I need to consider quantum mechanics when I try to hit the ball with a bat? 6. The radius of a H-atom is 120 pm. If the speed of an electron in the H-atom is known, within 0.01%, to be c/137, do I need to describe the electron using quantum mechanics? 6 7. A Nz molecule is confined to a cubic box with sides 1 m in length. If it has an energy of 6x102 J, is it appropriate to describe the Nz molecule using classical mechanics? (E = p/2m)