The buoyant force on a fully submerged object always points

Answer: Up Buoyancy is a net upward pressure force from the fluid (pressure increases with depth, so bottom pressure exceeds top pressure).

The diagram shows a submerged block in static equilibrium, held in place by string tension T, with buoyancy FB and weight W acting on it. Which equation correctly relates these forces?

Answer: T + FB = W Equilibrium (up positive): T + FB - W = 0 \Rightarrow T + FB = W (assuming the block is denser than the fluid so the string must pull up to keep it from sinking).

For a column of incompressible liquid, gauge pressure plotted against depth gives a straight line. Its slope is

Answer: \rho g P = \rho g h, so the slope of P-vs-h equals \rho g.

AP Physics 1 · Topic 8.3

Fluids and Newton's Laws (Buoyancy) Practice

Part of Fluids.(TOP-8.C)

Practice questions

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Sample questions

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Sample 1difficulty 1/5
$The buoyant force on a fully submerged object always points$
- A
  $Toward the deepest end$
- B
  $Down$
- C
  $Up$
  check_circle
- D
  $Horizontal$
Why
$Buoyancy is a net upward pressure force from the fluid (pressure increases with depth, so bottom pressure exceeds top pressure).$
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Sample 2difficulty 2/5
$T$
- A
  $T + F_B = W$
  check_circle
- B
  $T + W = F_B$
- C
  $T = F_B + W$
- D
  $T = W - F_B$
Why
$T + F_B - W = 0 \Rightarrow T + F_B = W$
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Sample 3difficulty 2/5
$For a column of incompressible liquid, gauge pressure plotted against depth gives a straight line. Its slope is$
- A
  $\rho/g$
- B
  $g$
- C
  $\rho g$
  check_circle
- D
  $\rho$
Why
$P = \rho g h$
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Sample 4difficulty 2/5
$0.50~\text{kg}$
- A
  $10~\text{N}$
- B
  $5.0~\text{N}$
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- C
  $0$
- D
  $2.5~\text{N}$
Why
$F_B = m g = 5.0~\text{N}$
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Sample 5difficulty 2/5
$600~\text{kg/m}^3$
- A
  $0.50$
- B
  $0.80$
- C
  $0.60$
  check_circle
- D
  $0.40$
Why
$V_\text{sub}/V = \rho_\text{wood}/\rho_\text{water} = 600/1000 = 0.60$
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