## 2 Physics word problems

Hello gentlemen good afternoon, I'm a newbie on this forum I have been scratching my head all weekend on how to do these problems. I am wondering if someone could show me the right way.

Q1) A motor-pump set lifts 25m3 of water in 6 minutes through a vertical height of 5 cm. The efficiency of the pump is 75% and the efficiency of the motor is 85%.

1.) Calculate the kW input to the motor.
2.) Motor HP (Calc. value)
3.) Cost of running the system for 8 hrs (The cost per kWh is .10 cents)

Q2) Will be revealed after the first one to avoid confusion :)

1. The problem statement, all variables and given/known data
Well I've given all known data I was given so that's met.

2. Relevant equations
Not sure, perhaps the word problem already encompasses the relevant equations already.

3. The attempt at a solution
Well my attempt was, for "1) Calculate kW input to the motor."
25,000kg * 9.81 = 245,250 N
245,250 * 0.05m / 360sec = 34.0625 Watts output to the motor
Multiplying both eff. to come up with a combined .75 * .85 = 0.6375 %
34.0625 / 0.6375 = 54.4314 Watts or 0.053 kW input to the motor

I'm not sure if this is correct, I haven't moved onto 2) and 3) because of said reason.

Regards,
Waffles
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 Quote by phinds You need to post this in the proper format for a homework problem. Please read the forum rules.
I hope this suffices what was required to ask a question on this subforum.

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