ElectricPavlov

10 marbles   3 are striped    7 are not       7 out of 10     7/10

H = 0 when he smacks the water in a big ol' belly flop:

0=-16t^2+15t+12           

       a = -16    b = 15     c = 12   for the Quadratic Formula

\(t = {-b \pm \sqrt{b^2-4ac} \over 2a}\)

\(t = {-15 \pm \sqrt{15^2-4(-16)(12)} \over 2(-16)}\)

 if you do the calculation,      t =    15/32   +  \(\sqrt{993}\) /32      = 1.4535 seconds

You're welcome.....   

I have no idea which current the question is asking about......I assumed both since it did not specify.....

It appears you have "A'" correct

B) if the pump is 72 % efficient....it wastes 28% of the power supplied to it to pump the water ( friction/heat noise vibration etc)

         .72 x  = 858.37

            x = power required = 858.37/.72 = 1192.2 watts required         if 28% is wasted

If you did the first parts A and B correctly

  know that   electricl watts =   V * I        where v = volts    I = current

     858.37 w = 220 v   * I

        I = 3.9 amperes

   B)   If answer A is correct , this should be   858.37/.72 = 1192.2 watts

                    1192.2 watts = 220 v * I

                        I = 5.42 amperes

See this question for methodology to check your  'A' answer:

https://web2.0calc.com/questions/any-help-would-be-appreciated-thank-you_1

Similar to the other water pumping problem

Mass of 1000 liters of water = 1000 kg

F = mg   =   1000 kg * 9.81 m/s² = 9810 N

W = F * d = 9810 N * 20 m = 196200 j

Power = work /time = 196200j / 60 sec = 3270 watts

50% efficient means 50% is wasted..... it will take twice as much power to pump the water =   2 * 3270 = 6540 watts

80% efficient  :    3270 / .8 = 4087.5 watts

12 gms / 6.023 * 10 ²³ atoms    =    1.99 x 10^-23    gram per atom

2.5 cubic meters of water has a mass of    2500 kg

Force = mg =  2500 kg   *  9.81 m/s^2  = 24525 N

work = f * d   =   24525 N * 12.5 m = 306562.5 j

power = work / time     =   306562.5 j / 30 sec      watts

work = force x distance

work = 750 x 15   j