Upthrust

• What primarily causes pressure on an object submerged in water?

  Surrounding water molecules colliding with it
• How does pressure change as an object moves deeper in water?

  Pressure increases due to more water above
• What determines the pressure in a liquid?

  Density of the liquid and gravitational field strength
• What is the formula for pressure in a liquid?

  Pressure = height × density × gravitational strength
• If the height of the liquid column is 20 meters, density is $1000 \text{ kg/m}^3$, and gravitational strength is $9.8 \text{ m/s}^2$, what is the pressure?


  Pressure = $196000 \text{ Pa}$
• What is the pressure at a depth of 90 meters with the same density and gravitational strength?

  Pressure = $882000 \text{ Pa}$
• How do you calculate the change in pressure when moving from 20 meters to 90 meters?

  Change in pressure = $686000 \text{ Pa}$
• What is up thrust in relation to submerged objects?

  It is the upward force exerted by surrounding water
• Why does a submerged box experience a larger upward force at the bottom?

  Because it is deeper than the top
• What determines whether an object floats or sinks?

  Comparison of up thrust and object's weight
• What happens if the weight of an object is larger than the up thrust?

  The object sinks
• How can we determine if an object will float without calculating up thrust and weight?

  By comparing densities of the object and liquid
• If an object is denser than water, what will happen?

  The object will sink
• If an object is less dense than water, what will happen?

  The object will float
• What factors affect the pressure in a liquid?

  • Depth of the liquid
  • Density of the liquid
  • Gravitational field strength
• What are the conditions for an object to float or sink?

  • If up thrust > weight, it floats
  • If weight > up thrust, it sinks
• What is the relationship between density and buoyancy?

  • Denser objects sink
  • Less dense objects float