Please do not answer these, just give hints A block of mass M is connected to a second block of mass m by a linear spinrg of natural length 8a. When the system is in equilibrium with the first block on the floor, and with the spring and second block vertically above it, the length of the spring is 7a. The upper block is then pressed down until the spring has half its natural length and is then released from rest. Show that the lower block will leave the floor if M<2m. A simple but violent reaction is H+H->H2+5eV. However when two electrons collide in free space they simply bounce apart. Can you prove this, using conservation of energy and momentum, i.e. show that a contradiction results.