Forces and dynamics - Physical Processes in Earth and Environmental Sciences - page 42

F total = - ( Σ m ) g Total force acting on an imaginary

plane surface above elevation of 7 km

Sectional view

+7 km +7 km

m 1 gm .. gm .. gm .. gm .. m .. gm .. gm .. gm n g

F

The body force acting on a surface
defines a surface force, given as the
total mass acting on the surface times
gravity

Plane view

Conceptual force field (spatial variation of surface force)
acting on the 7 km elevation plane below Everest

Fig. 3.8 Body force of Everest acting on a horizontal plane at 7 km elevation.

b

b

Fig. 3.9 These 20 kg volcanic bombs (b) were thrown upwards 100 m from a volcanic vent to attain an impact velocity of some 44 m s 1 in
moist soft volcanic ash, whereupon their momentum p :

880 kg m s 1
was totally destroyed upon impact. The resultant force, about 196 N, was sufficient for the bombs to penetrate and deform the layered ash to
a depth of some 0.4 m. Tenerife, Islas Canarias.

p mu