Walking Underwater
The final scene which will be examined is the famed walking underwater scene, located near the end of the film. In this scene, Captain Barbossa has taken Will Turner to the cursed treasure of Cortez, the chest of coins which gave Barbossa and his crew the dreaded curse to roam the seas as the undead. Barbossa hopes that with Will’s blood he can lift the curse bringing him and his men back to the living.
Just before Barbossa cuts Will’s throat, spilling his blood and lifting the curse, an unexpected visitor arrives, Captain Jack Sparrow. Captain Sparrow joins Barbossa at the chest and tells him and his crew that the Royal Navy is aware of their presence and has stationed a ship just offshore waiting to commence a surprise attack on the pirates. Captain Barbossa then tells his men to “take a walk”. In the next scene Barbossa's crew are seen walking underwater towards the British ship where they would turn the tables and form a surprise attack on the British (this walk can be seen in the video clip above). The pirates in this scene seem completely free of the force of buoyancy allowing them to walk on the floor of the ocean. Assuming the pirates masses stay the same, (they do turn into skeleton monsters) it is revealed that this Physic has been overlooked in production.
The pirates in Barbossa’s crew all have varying shapes and sizes, therefore they all have different force magnitudes acting on them. Since analyzing each pirate would prove difficult I decided to select a body size of six feet in height with a medium build. When running these numbers through a BMI calculator, it is noted that the mass of a man this size is 170 pounds or 77 kilograms. The force of gravity acting on a man this size can be seen below.
Fg=mg
=77(9.8)
= 755 N
According to Newton’s first law, if there is no external unbalanced force on an object that object will remain at its state of rest or current velocity. Therefore, in order for the pirates to sink they must have a force of buoyancy smaller than 755 N and in order for the pirates to float the force of buoyancy must be equal to 755 N. The calculation of the force of buoyancy on a man of this size can be seen below.
˜density of man= 1000kg/m^3
density of water= 1000kg/m^3
volume of man= m/dman
=77kg÷1000kg/m^3
= 0.077m^3
Volume of water displaced by man = to the volume of the man= 0.077m^3
Weight of water displaced by man = Force of Buoyancy
Weight of water displaced= vman(dwater)(g)
=0.077(1000)(9.8)
= 755 N
Force of Buoyancy= 755 N
The force of buoyancy and force of gravity on the man are equal in magnitude and opposite in direction.
Just before Barbossa cuts Will’s throat, spilling his blood and lifting the curse, an unexpected visitor arrives, Captain Jack Sparrow. Captain Sparrow joins Barbossa at the chest and tells him and his crew that the Royal Navy is aware of their presence and has stationed a ship just offshore waiting to commence a surprise attack on the pirates. Captain Barbossa then tells his men to “take a walk”. In the next scene Barbossa's crew are seen walking underwater towards the British ship where they would turn the tables and form a surprise attack on the British (this walk can be seen in the video clip above). The pirates in this scene seem completely free of the force of buoyancy allowing them to walk on the floor of the ocean. Assuming the pirates masses stay the same, (they do turn into skeleton monsters) it is revealed that this Physic has been overlooked in production.
The pirates in Barbossa’s crew all have varying shapes and sizes, therefore they all have different force magnitudes acting on them. Since analyzing each pirate would prove difficult I decided to select a body size of six feet in height with a medium build. When running these numbers through a BMI calculator, it is noted that the mass of a man this size is 170 pounds or 77 kilograms. The force of gravity acting on a man this size can be seen below.
Fg=mg
=77(9.8)
= 755 N
According to Newton’s first law, if there is no external unbalanced force on an object that object will remain at its state of rest or current velocity. Therefore, in order for the pirates to sink they must have a force of buoyancy smaller than 755 N and in order for the pirates to float the force of buoyancy must be equal to 755 N. The calculation of the force of buoyancy on a man of this size can be seen below.
˜density of man= 1000kg/m^3
density of water= 1000kg/m^3
volume of man= m/dman
=77kg÷1000kg/m^3
= 0.077m^3
Volume of water displaced by man = to the volume of the man= 0.077m^3
Weight of water displaced by man = Force of Buoyancy
Weight of water displaced= vman(dwater)(g)
=0.077(1000)(9.8)
= 755 N
Force of Buoyancy= 755 N
The force of buoyancy and force of gravity on the man are equal in magnitude and opposite in direction.
Free body diagram of forces
Since these two forces are opposing each other and are equal in magnitude, the pirates in reality will float on the surface of the water. They will not sink as there is no external unbalanced force bringing them to the bottom of the ocean. Since this did not happen in the film it is another example of bad physics.