3. Four men lift a 500 kg box to a height of 1 m and hold it without raising or lowering it.
(i) How much work is done by the men in lifting the box?
(ii) How much work do they do in just holding it?
(iii) Why do they get tired while holding it? (Take, g =10 ms=2)
Answers
Answer:
Given, m = 250kg, height (h) = 1 m and acceleration due to gravity g = 10 ms-2
(a) Work done by the man in lifting the box
W = Potential energy of box W = mgh
W = 250 x 1×10= 2500 J
(b) Work done is zero in holding a box, because displacement is zero.
(c) In holding the box, the energy of man loses. Due to loss of energy he felt tired.
B.w= f cos0s
w=0
because force and displacement are perpendicular to each other
a.) p.e= mgh
p.e=250×10×1
p.e=2500j
c) they get tired holding it long because they handle the gravitational force acting on box in downwards direction
Explanation:b.w= f cos0s
w=0
because force and displacement are perpendicular to each other
a.) p.e= mgh
p.e=250×10×1
p.e=2500j
c) they get tired holding it long because they handle the gravitational force acting on box in downwards direction
Step-by-step explanation: