A pump forces 12kg of water through a hose every minute. If the water is being raised vertically through 20m and ejected at the nozzle at 10m/s, calculate the power of the pump.

Mass of water, $m = 12 \text{ kg}$
Time, $t = 1 \text{ minute} = 60 \text{ s}$
Vertical height, $h = 20 \text{ m}$
Ejection velocity, $v = 10 \text{ m/s}$
Acceleration due to gravity, $g = 9.8 \text{ m/s}^2$

The power of the pump is $\boxed{\text{49.2 W}}$.

11. Determine the manometer which will have the lowest level between P, Q and R in the figure below. Explain your answer. [assume the water is flowing continuously from the tap to the tap to the outlet.]

Manometer Q will have the lowest level.

Explanation:
According to the principle of continuity, as water flows through the pipe, its speed increases where the cross-sectional area of the pipe is smaller. At point Q, the pipe is narrower than at P or R, so the water flows fastest at Q.
According to Bernoulli's principle, for a horizontal flow, where the fluid velocity is highest, the pressure is lowest. Since the water velocity is highest at Q, the pressure at Q will be the lowest. A lower pressure in the pipe means the water level in the manometer connected to that point will be lower.

12. A block of metal A having a mass 40kg requires a horizontal force of 100N to drag it with uniform velocity along a horizontal surface. Calculate the co-efficient of friction.

Mass of block, $m = 40 \text{ kg}$
Horizontal force, $F = 100 \text{ N}$
Acceleration due to gravity, $g = 9.8 \text{ m/s}^2$

Since the block is dragged with uniform velocity, the net force on it is zero. This means the applied horizontal force is equal to the force of friction.

On a horizontal surface, the normal force ($N$) is equal to the weight of the block.

The force of friction is given by the formula $F_f = \mu N$.

The coefficient of friction is $\boxed{\text{0.255}}$.