Question

While loading a truck, a man lifts boxes of 100 N each through a height of 1.5 m.

i) How much work does he do in lifting one box?

ii) How much energy is transferred when one box is lifted?

iii) TIf the man lifts 4 boxes per minute,at what power is he working? (g=10m/s^2)​

Answer 1

Given :

• Weight of box ( W ) = 100 N
• Height ( h ) = 1.5 m
• gravity ( g) = 10 m/s²

Solution :

Case 1 :

$\boxed{\sf \blue{Work = Force \times Displacement}} \\ \\ \sf Work = 100 \times 1.5 \\ \\ \sf \underline{ \sf Work = 150 \: J}$

Case 2 :

The work done against gravity is stored in the box in the form of potential energy. So, energy transferred when one box is lifted is 150 J

Case 3 :

Work done in lifting 4 box

$\sf 150 \times 4 = 600 \: j$

$\sf time \: taken \: (t) = 1 min = 60 \: sec \\ \boxed{ \sf \green{ power = \frac{work}{time} }} \\ \\ \sf Power = \frac{600}{60} \\ \\ \underline{ \sf Power = 10 \: W}$

Power of the man is 10 W