AP Physics 1 fluids buoyancy and pressure study guide

Define density in fluids.

Density is mass per unit volume, expressed as ho = \frac{m}{V}, where m is mass and V is volume.

True or False: Fluids exert pressure in all directions.

True. Fluids exert pressure equally in all directions due to their ability to flow.

Fill in the blank: The unit of pressure in the SI system is ___.

Pascal (Pa) - 1 Pa = 1 N/m².

What is the formula for pressure?

Pressure (P) is defined as P = \frac{F}{A}, where F is force and A is area.

Compare viscosity and density.

Density measures mass per volume; viscosity measures a fluid's resistance to flow.

What does a high viscosity indicate?

High viscosity indicates a fluid flows slowly, e.g., honey vs. water.

State the equation for hydrostatic pressure.

Hydrostatic pressure is given by P = P_0 + ho gh, where P_0 is atmospheric pressure.

True or False: Temperature affects viscosity.

True. Increasing temperature generally decreases viscosity in liquids.

What is the relationship between pressure and depth in a fluid?

Pressure increases with depth: P = P_0 + ho gh.

Fill in the blank: The density of water is approximately ___ kg/m³.

1000 kg/m³.

What is gauge pressure?

Gauge pressure is the pressure relative to atmospheric pressure, calculated as P_g = P - P_{atm}.

How does viscosity affect fluid flow?

Higher viscosity results in slower fluid flow and greater energy loss due to friction.

State the SI unit for viscosity.

The SI unit for viscosity is the Pascal-second (Pa·s).

What is the formula for specific gravity?

Specific gravity (SG) is defined as SG = \frac{ ho_{fluid}}{ ho_{water}}.

True or False: Fluids can only be liquids.

False. Fluids include both liquids and gases.

Give an example of a low viscosity fluid.

Water is a low viscosity fluid, flowing easily compared to syrup.

What is buoyancy?

Buoyancy is the upward force exerted by a fluid on an object immersed in it, allowing objects to float or rise.

State Archimedes’ principle.

An object submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid displaced.

True or False: Heavier objects always sink.

False: An object will float if its weight is less than the weight of the fluid it displaces.

Fill in the blank: The buoyant force equals ____.

The weight of the fluid displaced by the object.

What factors affect buoyancy?

Density of fluid, volume of object submerged, and the weight of the object.

How does density affect buoyancy?

A denser fluid provides a greater buoyant force. Objects less dense than the fluid float.

Consider a block of wood and a block of metal in water.

Wood floats due to lower density; metal sinks because it is denser than water.

Calculate the buoyant force on a 5 kg object in water.

Buoyant force = weight of displaced water = 5 kg × 9.81 m/s² = 49.05 N.

What happens if the volume of an object increases?

If the object's density remains less than the fluid's, the buoyant force increases, allowing it to float more easily.

True or False: A submerged object always experiences an upward force.

True: A submerged object always experiences an upward buoyant force regardless of its weight.

Define relative density.

Relative density is the ratio of an object’s density to the density of a reference fluid, usually water.

What is the formula for buoyant force?

Buoyant force $\displaystyle F_b = \rho_{fluid} \cdot V_{displaced} \cdot g$, where $\displaystyle V_{displaced}$ is the volume of fluid displaced.

Describe a real-world application of buoyancy.

Submarines adjust their buoyancy by controlling water intake to dive or surface.

Differentiate between buoyant force and weight.

Buoyant force is the upward force from fluid; weight is the downward force due to gravity.

Fill in the blank: An object will float if its ____ is less than the fluid's density.

Density.

What happens to the buoyant force as depth increases?

Buoyant force remains constant as it depends on the volume of fluid displaced, not depth.

How does temperature affect water density?

As temperature increases, water density decreases, affecting buoyancy of objects.

Calculate the weight of water displaced by a submerged object.

Weight = volume submerged × density of water × g (9.81 m/s²).

Explain why ice floats.

Ice is less dense than liquid water, so it displaces enough water to support its weight.

What is the effect of shape on buoyancy?

Shape influences the volume of fluid displaced, affecting the buoyant force experienced by the object.

What is Bernoulli's equation?

Bernoulli's equation states that for an incompressible, frictionless fluid, the total mechanical energy is constant: $\displaystyle P + \\frac{1}{2} \rho v^2 + \rho gh = \text{constant}$.

True or False: Fluid pressure decreases with increasing depth.

False. Fluid pressure increases with depth due to the weight of the fluid above.

Fill in the blank: In a fluid at rest, the pressure acts __________ in all directions.

equally

What are the units of fluid pressure?

Pressure is measured in Pascals (Pa), where $\displaystyle 1 ext{ Pa} = 1 ext{ N/m}^2$.

Compare laminar flow and turbulent flow.

Laminar flow: smooth, orderly; Turbulent flow: chaotic, unpredictable.

Cause → Effect: What happens when fluid velocity increases?

Pressure decreases in accordance with Bernoulli's principle.

What does the Venturi effect illustrate?

The Venturi effect illustrates that fluid speed increases and pressure decreases in a constriction.

Calculate the flow rate given area and velocity.

Flow rate $\displaystyle Q = A v$, where $\displaystyle A$ is area and $\displaystyle v$ is velocity.

True or False: Streamlines can cross each other.

False. Streamlines represent fluid flow direction and cannot intersect.

What is the continuity equation?

The continuity equation states that for an incompressible fluid: $\displaystyle A_1 v_1 = A_2 v_2$.

How does viscosity affect fluid flow?

Higher viscosity results in slower flow rates and greater resistance to movement.

What is the significance of the Reynolds number?

Reynolds number indicates flow regime: $\displaystyle Re < 2000$ (laminar), $\displaystyle Re > 4000$ (turbulent).

True or False: Fluid flow is only dependent on the fluid's density.

False. Fluid flow also depends on viscosity and pressure differences.

What is a pitot tube used for?

A pitot tube measures fluid velocity by comparing static and dynamic pressure.

Define hydrostatic pressure.

Hydrostatic pressure is the pressure exerted by a fluid at rest, calculated as $\displaystyle P = \rho gh$.

Fill in the blank: The __________ principle states that an increase in fluid speed decreases pressure.

Bernoulli

What is the relationship between pressure and volume in fluid dynamics?

According to Boyle's Law for gases, $\displaystyle P_1 V_1 = P_2 V_2$ (at constant temperature).

Describe how lift is generated in an airplane wing.

Lift is generated because air moves faster over the wing's curved top, creating lower pressure.

What is the role of surface tension in fluids?

Surface tension causes the fluid surface to behave like a stretched elastic membrane.

Explain Bernoulli's principle in fluid dynamics.

Bernoulli's principle states that in a steady, incompressible flow, an increase in the fluid's velocity occurs simultaneously with a decrease in pressure. - Applications: airplane wings, carburetors, and fluid meters. - Formula: $\displaystyle P + \frac{1}{2} ho v^2 + ho gh = ext{constant}$.