Liquid Pressure & Upthrust

• What are we going to calculate in this video?

  Pressure in a liquid and floating objects
• 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 is the relationship between liquid density and pressure?

  Denser liquids exert more pressure
• What determines the weight of an object in a liquid?

  Gravitational field strength and mass
• 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 kg/m³, and gravitational strength is 9.8 m/s², what is the pressure?

  196,000 pascals
• What is the pressure at a depth of 90 meters with the same density and gravitational strength?

  882,000 pascals
• How do you calculate the change in pressure when moving from 20 meters to 90 meters?

  Subtract pressure at 20m from 90m
• What is the change in pressure when moving from 20 meters to 90 meters?

  686,000 pascals
• What is up thrust in relation to submerged objects?

  Up thrust is the upward force on the object
• Why does a submerged box experience a larger upward force at the bottom?

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

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

  The object sinks
• What happens if the up thrust is larger than the weight of an object?

  The object floats
• How can we determine if an object will float or sink without calculating forces?

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

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

  The apple will float
• What factors determine the pressure in a liquid?

  • Depth of the liquid
  • Density of the liquid
  • Gravitational field strength
• What is the relationship between up thrust and weight in determining if an object floats?

  • Up thrust must be greater than weight for floating
  • Weight must be greater than up thrust for sinking
• How do you calculate pressure change with depth?

  1. Calculate pressure at both depths
  2. Subtract the two pressures
• What is the significance of comparing densities for floating and sinking objects?

  • Determines if an object will float or sink
  • Less dense objects float, denser objects sink