A student submerges two identical pressure probes in a large, open tank of fresh water.
• Probe X is pressed flush against a vertical wall of the tank so that its sensing face is oriented horizontally.
• Probe Y is pressed against the horizontal bottom of the tank so that its sensing face is oriented vertically upward.
Both probes are located at the same depth h below the free surface of the water.
Assume the water is at rest and has uniform density ρ. Neglect any effects of surface tension or probe size.
(a) Describe, in terms of molecular motion and collisions, how the water exerts force on the sensing face of either probe.
(b) Explain why the magnitude of the pressure measured by Probe X must be equal to that measured by Probe Y, even though the sensing faces are oriented differently.
(c) Discuss how your explanation in part (b) is consistent with pressure being a scalar quantity rather than a vector quantity.