Question

32) HOW IS THE POWER RELATED TO THE SPEED AT WHICH A BODY CAN BE LIFTED? HOW MANY KILOGRANMS WILL A MAN WORKING AT THE POWER OF 100W IS ABLE TO LIFT AT A CONSTANT SPEED OF 1 M/S VERTICALLY?

Answer 1

a) Power(P) = Force(F) × Velocity (V)
b) Given: P = 100 W ; V = 1 m/s
=> F = P/V = 100/1 = 100 N
Now, we know that F = mg
=> m = F/g = 100/10 = 10 kg

Answer 2

${\implies Power=\dfrac{Work\:done}{time}}$  

${\implies Power=\dfrac{mgh}{t}}$  

${\implies Power = m.g.\dfrac{h}{t}}$  

${\implies\dfrac{h}{t} = Speed}$

Hence

${\implies m=\dfrac{Power}{g\times Speed}}$

${\implies m = \dfrac{100}{10\times 1}}$

= 10 kg