A person weighing 500 N stands on their two feet. If the area of each foot is 0.018 m2, the pressure exerted on the ground can be calculated as:
Pressure = Force Area =
(2 x 0.018 m2) = 13,888.88 N/m2 500
If the same person was standing on one stiletto heel with an area of 0.0001 m2, then the pressure exerted would be:
Pressure = Force Area = 500
Elephants and stilettos Which would you rather stood on your foot?
a. A person weighing 600 N and wearing a pair of stilettos. The person stands on your foot with the stiletto heels, each of which has an area of 0.0001 m2.
b. An elephant weighing 38,000 N standing on one foot of area 0.12 m2.
Explain your answer. Describe the relationship
Copy the following sentences and circle the correct words to describe the relationships:
z A force applied over a (small/large) area results in a (big/small) pressure.
z Pressure is a measure of (force/area) per unit (force/area). Pressure is measured in (newtons per metre squared/newton metres).
Fig. 17.6.2 F n
Jellyfish stings are one of the fastest cellular processes in nature. The pressure generated when a jellyfish releases its stinging barbs into its prey is more than 15 giga N/m2. That is the same as the pressure exerted by a high-speed bullet!
0.0001 = 5,000,000 N/m2
17.6
Fig. 17.6.3
When a jellyfish releases its barbs into its prey, more than 15 giga N/m2 of pressure is generated
