Units (Solids, Liquids and Gases)
4 marks · NormalA metal can has holes at different heights, and water squirts out horizontally from each hole when filled. The can stands in a tray. Assume g = 10 N/kg.
Explain why the water squirts further from the lower holes than from the upper holes.
The bottom hole is 0.20 m below the water surface. If the density of water is 1,000 kg/m³, calculate the pressure difference between the surface and the bottom hole.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) The pressure is greater at greater depth, so more force pushes the water out of the lower holes, making the water squirt further. · must show Pressure increases with depth, Greater force causes more distance
(b) 2,000 Pa · must show Correct substitution in p = h × ρ × g
Common mistakes: Wrong value for g or density; Mixing up depth and height
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Mentions that pressure increases with depth in a liquid.
B2 (a) · 1 mark · Connects higher pressure with a greater force/distance of water squirting out.
M1 (b) · 1 mark · Correct substitute values into p = h × ρ × g.
A1 (b) · 1 mark · Correct answer (within tolerance) and unit.
Worked solution
a) The pressure at the bottom hole is greater because liquid pressure increases with depth. More pressure means more force behind the water, so it squirts out further.
b) p = h × ρ × g = 0.20 m × 1,000 kg/m³ × 10 N/kg = 2,000 Pa.