Respuesta :

Power is the rate of doing work.
∴ power=work-done /time taken

For a load been lifted up, 
work-done = mass×gravity×height
                  =mgh

so,  power = mgh/t
where t⇒time

When h is doubled and t is halved, the new power will be

Power-2 = mg2h ÷ 0.5t
              = 4(mgh/2)

That is to say, power-2(new power) is four time the initial power. 

The motor's power should increase with factor 4.

 

The power factor required to lift the beam twice as high in half the original time is : 4

Given that :

Power ( P ) = Work done / time  -- ( 1 )

Also work done for a lifted load

Work done = mgh  ( mass * gravity * height   )

Back to equation ( 1 )

Power ( p )  = mgh / time  --- ( 2 )

Considering the conditions given

When;  h = 2 * h  and t = 1/2 * t

Power becomes

New Power = m*g*2h / 1/2* t

             = 4( m*g*h / 2

Therefore we can conclude that The power factor required to lift the beam twice as high in half the original time is : 4.

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