CIE iGCSE Co-Ordinated Science P1.7 Pressure Exam Style Questions Paper 4
Question
Fig. 6.1 shows an electric pressure‑washer being used to wash a car.
(a) The pressure‑washer pumps water at a high pressure through a small nozzle.
The cross‑sectional area of the nozzle is 5.0 × 10–6m2.
The water leaves the nozzle with a pressure of 9.0 × 106Pa.
Calculate the force exerted by the water as it leaves the nozzle.
force = ……………………………………………… N
(b) The pressure‑washer uses a d.c. motor to pump the water out of the nozzle.
Fig. 6.2 shows a diagram of a simple d.c. motor.
(i) The arrows on Fig. 6.2 show the direction of the current.
Draw an arrow to show the direction of the force acting on the coil at the point labelled X.
(ii) Describe the function of the split‑ring commutator in a simple d.c. motor.
(c) After the car has been washed, droplets of cold water remain on the roof of the car.
After a few minutes, the droplets of water have disappeared.
(i) State the name of the process which causes the droplets of water to disappear.
(ii) Describe the process which causes the droplets of water to disappear in terms of molecules.
▶️Answer/Explanation
Ans :
6(a) (F=) P × A or 9.0 × 106 × 5.0 × 10–6 ;
(F=) 45 (N) ;
6(b)(i) arrow drawn upwards ;
6(b)(ii) provides an alternating current (in the coil) / current that changes direction every half-turn / to reverse the current every half turn/180° ;
allows coil to continue to turn (in the same direction) ;
6(c)(i) evaporation ;
6(c)(ii) the most energetic molecules ;
escape from the surface ;