plz answer this question according to five marks
Answers
Two farmers hold 100 kg sac at a height of 1 m .
(i) Amount of work done = mgh
m = 100 kg + 100 kg
= 200 kg
g = 10 m/s²
h = 1 m
Hence work = 200 kg × 10 m/s² × 1 m
= 2,000 J
The amount of work done is 2,000 J
(ii) Work = force × displacement
When the farmers just hold the sac , there is no displacement at all.
Hence :
work = force × 0
= 0
There is no work done by just holding the sac .
(iii) The farmer has to hold the sac against the weight of the sac .
Hence he uses some force and energy .
So after some time , he is exhausted because his energy is applied in holding the sac .
(iv) We know that :
kinetic energy while hitting = potential energy while dropping
==> 1/2 m v² = mgh
Cancel m both sides :-
==> 1/2 v² = gh
==> v² = 2gh
Given : g = 10 m/s²
h = 1 m
Hence v² = 2 × 10 m/s² × 1 m
==> v² = 20 m²/s²
==> v = √20 m/s
==> v = 2√5 m/s
The velocity of the sac will be 2√5 m/s
Hope it helps !
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Here the answers are
a.work = 2000J
b.then no work done
c.farmers lose energy hence they get tired
d.velocity = 2(root)5
Hope it helps
For explanation see the other answer