By Meghan Eisold

Many students at Colgate own
Nalgene water bottles. I have been told that they are indestructible and that
one would not even break if a car were to run over it. I decided to use physics
to determine if this statement is true. To begin, I calculated the cross-sectional area of the water
bottle and the force that the car would exert on it. I used these to determine
the stress on the water bottle.

Stress=F/A

A=cross-sectional area of Nalgene

L=20 cm (0.20 m)

W=9 cm (0.09 m)

A = L x W (contact area)

**A= 0.018 m**

^{2}
Force of average-sized car=ma

F=(1500kg)(9.8 m/s

^{2})**F= 14,700 N**

Stress =F/A

Stress= 14,700 N/0.018 m

^{2}
Stress= 816, 666
N/m

^{2}=**816,666 Pa (0.8166 MPa)**
Nalgene bottles are made of a material called Lenax
(polycarbonate), which has a compressive strength of 12,500 psi. To put this in
perspective, the compressive strength of a hard brick is about 12,000 psi. I
compared this compressive strength to the magnitude of stress on the water
bottle to determine if the bottle could withstand the force of the car.

Compressive strength of Lexan: 12,500 psi.

^{}
1 Psi = 6 894.75729 Pascals

12,500 Psi x (6894.757 Pa)/(1
Psi) = 861, 844, 662. 5 Pa

Compressive strength of Lexan
=

**861.4 MPa**
861.4 MPa > 0.8166 MPa

Based on these calculations, the stress exerted on the Nalgene
bottle by an average sized car is much smaller than the compressive strength of
Lexan (the material from which Nalgene bottles are made). This means that the Nalgene
bottle would not break under the force of an average sized vehicle. The actual
results may vary somewhat due to the arched shape of the Nalgene bottle.

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