# What work does a person need to do in order to lift a 9 kg bucket of water from a well 30 m

**What work does a person need to do in order to lift a 9 kg bucket of water from a well 30 m deep with the help of a gate with an efficiency of 90%?**

1. Let’s write down the condition:

S = 30 m

m = 9 kg

Efficiency = 90% = 0.9

A-?

2. Let’s compose a formula for finding useful work, taking the weight of a bucket of water as the force:

A floor. = F × S

F = P

P = mg

A floor. = mg × S

3. Substitute into the formula the numbers from the condition:

A floor. = 9 kg × 10 N / kg × 30 m

A floor. = 2700 J

4. From the efficiency formula, we derive the formula for finding the work expended and find the numerical answer:

Efficiency = A pol. / A zat.

A zat. = A pol. / Efficiency

A zat. = 2700 J / 0.9

A zat. = 3000 J

5. Let’s correlate the number with the answers and choose the correct one:

The answer is 2.