Question

A pump ligts 420kg of water every minute through a vertical height of 30m assume g=10N/kg. a) Calculate the potential energy (PE) gained by the water every minute. b) Explain why the energy needed operate the pump for one minute is greater than the value you have calculated in (a
)

Answer 1

Answer:

Given:

Mass of water pumped = 420 kg

Height to which it is pumped = 30 m

g = 10 m/s²

To find:

• Potential Energy gained by water

Concept:

Gravitational force is an conservative force. That's why , work done against the gravitational force becomes stored in the body as gravitational potential energy.

That's why the water achieve Potential energy at that height. The work done by pump is converted to Potential energy stored in the Water.

Calculation:

Potential energy gained by water :

$= m \times g \times h$

$= 420 \times 10 \times 30$

$= 126000 \: J$

$= 126 \: kJ$

So final answer is :

$\boxed{ \blue{ \huge{ \bold{PE = 126 \: kJ }}}}$

The pump actually takes more energy as compared to the theoritical (calculated) work because no machine is 100% efficient.

A certain amount of supplied energy gets lost from the machine as heat energy and the rest is used as work.

This can be better understood while reading Thermodynamics.

Answer 2

$</p><p>\huge{\pink{\tt{Hello!!! }}}$

$</p><p>\orange{\tt{Step-By-Step-Explaination \: - }}$

$</p><p>\tt{\red{Given \: - }}$

• Mass of Water Lifted = 420 kg.

• Vertical Height = 30m.

• g = 10N/Kg.

$</p><p>\tt{\therefore{\blue{Potential \: Energy \: - }}}$

$\tt{ \red{ P.E. \: = \: mgh \: = 126000 \: J \: }}$

There is a huge difference between theoritical energy and actual energy.

No machine can be 100% efficient.