When you hold your hand palm-up, the atmosphere exerts a force of about 800 N on the palm of your hand. Comparing this force with
I. the force on the back of the hand,
II. the force on the palm when you are holding your hand vertical,
III. the force on the palm when it is palm-down
A) It is equal to I but different from II and III
B) it is different from I, II, and III
C) It is equal to II and III but different from I
D) They are all equal
Why would they be different? What is Pascal's principle?
To determine the answer, let's consider each case and compare the forces.
I. Force on the back of the hand:
When your hand is palm-up, the force on the back of your hand is due to the pressure difference between the atmospheric pressure and the pressure of the air between the palm and back of your hand. Assuming the pressure between the palm and back of your hand is negligible, the force on the back of your hand would be zero. Therefore, the force on the back of the hand is different from the given 800 N.
II. Force on the palm when the hand is held vertical:
When you hold your hand vertical, there is no significant pressure difference between the atmospheric pressure and the air pressure inside your hand. Thus, the force on the palm would also be zero. Hence, the force on the palm when the hand is vertical is different from the 800 N mentioned.
III. Force on the palm when it is palm-down:
When your hand is palm-down, the atmospheric pressure exerts a force on the palm. This force is the same 800 N mentioned in the question.
Considering the above explanations, we can conclude that the force on the palm, when your hand is held palm-up, is different from the forces on the back of the hand and the palm when it is held vertical. However, it is equal to the force on the palm when it is palm-down.
Therefore, the correct option is A) It is equal to I but different from II and III.
Pascal's principle states that when pressure is applied to an enclosed fluid, the pressure increase is transmitted equally to all parts of the fluid. This principle is the foundation of how hydraulic systems work, where a small force applied to a small area can be amplified to create a larger force on a larger area. Pascal's principle is relevant to studying fluid mechanics and hydraulic systems.