JEE · Physics · Mechanical Properties of Fluids doubts
8 doubts found
When I half-cover a tap or hose with my thumb, why does the water suddenly spray out much faster?
This is the equation of continuity, A1v1 = A2v2.
Why does the roof of a house sometimes get lifted off during a storm even though the wind blows sideways, not up?
Fast-moving air over the roof lowers the pressure there (Bernoulli's principle: faster flow → lower pressure).
A steel ship floats but a steel needle sinks — both are steel, so how?
Floating depends on average density, not the material alone.
How does a small hydraulic jack let one person lift a whole car?
By Pascal's law, pressure applied to an enclosed fluid is transmitted equally everywhere.
Why does a raindrop or a skydiver stop speeding up and fall at a steady 'terminal' velocity?
As the drop speeds up, the upward viscous drag of the air (which grows with speed) and buoyancy increase until they exactly balance gravity.
Why does water climb up a thin glass tube on its own, while mercury actually goes down?
It's capillarity, set by whether the liquid wets the glass.
Why can a water strider (and even a steel pin) rest on water without sinking?
The water surface behaves like a stretched elastic film because of surface tension — molecules at the surface are pulled inward, so the surface resists being pierced.
Why is a dam built much thicker at the bottom than at the top?
Water pressure grows with depth, P = ρgh, so the deepest water pushes hardest on the wall.