K.C.S.E Physics Q & A - MODEL 2012PP1QN19

K.C.S.E Physics Q & A - MODEL 2012PP1QN19

​(a) Figure 14 shows a lift pump.

​Explain why, when the piston is:
(i) pulled upwards, valve A opens while valve B closes. 
(ii) pushed downwards, valve A closes while valve B opens. 
(b) After several strokes, water rises above the piston as shown in Figure 15.

State how water is removed from the cylinder through the spout.
(c) A lift pump can lift water to a maximum height of 10 m. Determine the maximum height to which the pump can raise paraffin.
. (take density of paraffin as 800 kgm^-3 and density of water as 1000 kgm^-3).
(d) State one factor that determines the height to which a force pump can lift water.

answers

(a) (i) Valve B rests under its own weight;
 pressure in the cylinder decreases and water rises into the cylinder pushing the valve open; 
(ii) Valve A rests under its own weight and the weight of the water; high pressure is created in the region between valve A and valve B forcing valve B to open; 
(b) The water is lifted up by the piston ad comes out through the spout; 

​(d) - Force applied on piston (during downstroke);
- Ability of the parts of the pump to withstand the pressure of the liquid column;