hit the wall...

ok what i have set up is say a cube and i walk over to it and i pick it up and i can carry it around in front of me and then drop it and all of that is working just fine i do it by

mouse over
mouse left button “True” and parent to hand

note the hand is basically an empty witch is parented to the camera but anyways
what im looking to do now is make it so that the objects i pick up collide into walls and floors because right now when i pick them up i can look down and put them right threw the floor or threw a wall and so i want them to keep the same dynamics as when there not parented to the hand. anyways is this possible and can someone help me with this