You are lying in bed and want to shut your bedroom door.You have a bouncy “superball” and a blob of clay, both withthe same mass. Which one would be more effective to throwat your door to close it?(a) The superball.(b) The blob of clay.(c) Both the same.(d) Neither will work.

(d) In terms of the impulse-momentum theorem, describe the underlying physics in the benefit of built in automotive crumple zones in medium speed collisions. (e) What is the difference between an elastic and an inelastic collision?

b) A vertical pile of mass 150 kg is driven 120 mm into the ground by the blow of a 1100 kg hammer, which falls through 800 mm. assuming the hammer and pile remain in contact, determine the following: i) The velocity of the hammer just before impact ii) The velocity immediately after impact iii) The resistive force of the ground, assuming it to be uniform

A railroad car of mass M moving at a speed v 1 collides and couples with twocoupled railroad cars, each of the same mass M and movingin the same direction at a speed v 2. (a) What is the speed vf ofthe three coupled cars after the collision in terms of v 1 and v 2?(b) How much kinetic energy is lost in the collision? Answerin terms of M, v 1, and v 2.

Moderating a Neutron In a nuclear reactor, neutrons released by nuclear fission must be slowed down before they can trigger additional reactions in other nuclei. To see what sort of material is most effective in slowing (or moderating) a neutron, calculate the ratio of a neutron's final kinetic energy to its initial kinetic energy, Kf/Ki, for a head-on elastic collision with each of the following stationary target particles. (Note: The mass of a neutron is m=1.009u, where the atomic mass unit, u, is defined as follows: 1u=1.66×10−27kg.) An electron (M=5.49×10−4u) Express your answer using four significant figures.Kf/Ki=