Pupil sheet · Pressure

Pressure — final check

Name ______________________ Date ____________

Work alone, with the lesson closed. Answer every question; there are no hints.

1. define / calculate / state / explain

A garden chair stands on a soft lawn on four legs. With a person sitting on it, it pushes on the lawn with a force of 900 N. The lawn gives way under a pressure of more than 60 000 Pa. (a) Define pressure. (b) Calculate the smallest total area of the four legs, in cm², that stops the chair sinking in. (c) A heavier person sits on the same chair. State how the smallest safe area changes, and explain why.

(a) Definition

(b) Smallest area in cm²

2. explain / calculate / determine

A factory stores apple juice of density 1050 kg/m³ in a tall tank. The juice is 5.2 m deep. A pressure sensor is fixed to the wall of the tank, 1.2 m above the bottom. (a) Juice is drawn off until it is 3.2 m deep. The sensor is not moved. Explain what happens to the reading of the sensor. (b) Supplement. Take g = 9.8 N/kg. Calculate the pressure of the juice, not counting the pressure of the air, at the bottom of the full tank. (c) Supplement. A second tank holds syrup of density 1300 kg/m³, 4.4 m deep. Determine which tank, the full juice tank or the syrup tank, has the greater pressure of the liquid at the bottom.

(a) The reading as the level falls

(b) Supplement: pressure at the bottom