# Pyramids homework 2

Mar. 13, 2012
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### Pyramids homework 2

1. The great pyramid at Giza Humans like building things. A career in engineering begins with AS9040 Aspects of mechanics. Building managers overseeing pyramid building contracts 4,500 years ago understood this stuff.
2. The outer blocks are rough The pyramids used to be dressed with smooth limestone blocks
3. The great Pyramid Built for Pharaoh Khufu
4. The Physics of Construction • Huge blocks of stone have to be moved horizontally along the ground from the quarry and vertically upwards as the pyramid takes shape • The horizontal force needed to drag the blocks of stone has to overcome frictional forces. • To lift a block vertically upwards the weight force due to gravity has to overcome.
5. Dragging against friction • The density of porous limestone used in construction is 2,500kgm-3 • The great Pyramid consists of over 2,500 million blocks of limestone with masses ranging from 2 to 70 tons
6. Question 1 It is about 800 metres from the quarry to the base of the great pyramid. Experiments have shown that sleds with 2.5 ton blocks can be drawn at a speed of 0.25ms-1. a. How long will it take to drag 1 block from the quarry to the base of the pyramid. b. A slave can take the sled back to the quarry in 10 minutes, Calculate his speed in metres per second
7. Question 2 • The maximum force that a slave could exert when dragging a block in the heat of the Egyptian sun is about 300 N. • 8 slaves would be used to drag each block on its sled. Calculate the force of friction that needs to be overcome as the sled is dragged at a steady speed 8 slaves dragging the Frictional block force opposing motion
8. Question 3 • What is the total work done moving the 2.5 ton block from the quarry 800 metres to the base of the pyramid • What was the total work done by each slave
9. Lifting against gravity 146.5m in height Question 4 a) The height of the pyramid is 146.5m The mass of each block is 2,500Kg. Calculate the total work done in raising the final block to the top of the pyramid. b) How much gravitational energy does it have?
10. • blocks 0.8 m square by 1.6 m long and weighing 2.5 tons, showed how 18 men could drag the block over a 1-in-4 incline ramp, at a rate of 18 meters per minute