Question

Help please with steps ?

Answer 1

C.

Explanation:

We know power `P` = work done/time=`W/t`

Here, work will be done to supply the required amount of potential energy for that amount (`m`) of water vapour to be at height (`h=2 Km`)

So, `W=mgh`

`P=2×1000` watt

So, `t=W/P`

So, `t=(mgh)/P=(2.66×10^7×10×2000)/(2000)=2.66×10^8 s`

This is approximately equals to 8 yrs and 97 days.

Answer 2

C

Explanation:

Let's think about formulae that we can use.

We know a power (2 kW), a mass (2.66 `times 10^7` kg), and a height (2 km) and we want to know a time.

Power is energy over time, so that means we know the time if we know the energy.

The energy we can find out using the mass and the height because the energy is gravitational potential energy! Therefore,

`E = mgh = (2.66 times 10^7\ kg)(9.8 m/s^2)(2 times 10^3\ m)`
`= 5.21 times 10^11 \ J`

At 2 kW, that means our time to pump would be
`t = E / P = (5.21 times 10^11 J) / (2 kW) = 2.6 times 10^8 s approx 8` years and some change; C