To what height can a 400 W engine lift a 100 kg mass in 3s? (h= 1.22 m) 



Given:

Power of the engine = 400 W
Mass of the engine = m = 100 kg
Time = t = 3 s 
Value of g = 9.8 ms⁻²

To Find:

Height  = h = ?


Solution:

Using the formula of Power

P = `\ frac{W}{t}`  ------------(1)

But work done = W = Gain in P.E. = mgh, So,

P = `\ frac{mgh}{t}` 

Or 

h = `\ frac{Pt}{mg}` 

putting values

h = `\ frac{400 W ｘ 3 s}{100 kg ｘ 9.8 ms⁻²}`      [W (watt) = kg m² s⁻³]


h = 1.22 m ------------------Ans


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