Draw pressure forces on a completely submerged rectangular block. Starting with the difference between top and bottom pressures, derive U=ρgV. Explain what happens to U if the block is lowered without changing its volume in a liquid of constant density.

Question

Accepted Answer

Lower pressure is greater by ρgh. Net vertical fluid force=(p_bottom−p_top)A=ρghA=ρgV upward. At greater depth both pressures increase equally, so U is unchanged. Pressure forces act normally to each face; side resultants cancel. The bottom pressure exceeds the top by ρgh. Subtract forces, not pressures alone: U=(p_bottom−p_top)A. Use V=Ah to obtain U=ρgV. State unchanged upthrust at greater depth and justify using unchanged pressure difference.

Explain where upthrust comes from

Draw pressure forces on a completely submerged rectangular block. Starting with the difference between top and bottom pressures, derive U=ρgV. Explain what happens to U if the block is lowered without changing its volume in a liquid of constant density.

What a complete response should do

Your self-assessment