1. Molasses explosion 1919 Boston

2. Solution tic tac toe

3. 8 7 10 9 4 1 2 11 5

4. The phenomena are:. the Roman arch
The phenomena are: *the Roman arch *the (Nubian) vault To build an arch, a scaffold is needed to support it during construction The vault is built without using a scaffold. *The invention not mentioned is the dome NOT post and beam! * Glue joints, form joints, pin joints * The joint between the mud bricks is a glue joint

5. The three systems are:
Vierendeel truss (rectangular pattern), relying on stiff joints that transmit loads in bending
Triangulated truss that transmit loads through pin-joints (that can rotate, so no moment can be transmitted ) allowing the members to transmit only tension and compression, and the pins shear, but no moments.
Pure tension catenary system

6. Put the books in a stack
Put the rope around bottom, both sides and top, tie the rope tightly
Tip over to act as a horizontal, externally rope-reinforced book beam
The analogy in the real world of construction the post-tensioned or pre-stressed reinforced concrete beam

7. The issue here is buckling: under high compressive stress a column starts to deform, so that the compressive forces start acting in bending, which, if allowed to continue will (very suddenly) lead to the collapse of the column, which will result in the whole building falling down..
In Wells cathedral they stabilized the buckling columns with an ingenious system of cross arches- an upside down one on top of a regular one

8. An earthquake can cause the earth or rock below a building to move violently in a lateral direction, but sometimes also in a vertical or slanted directions.
Bracing the building by the use of rigid joints (Vierendeel system) or diagonal bracing (triangulated truss system) or rigid cross walls will help the building resist the earth quake forces.
Disconnecting the building form the foundation through sliding plates or rubber pads makes it possible to avoid the building being subjected to the lateral forces.