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.
The outer blocks are rough
The pyramids used to be dressed with smooth limestone blocks
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
• 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.
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
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
• 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
dragging the Frictional
• 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
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
b) How much gravitational energy does it have?
• 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