A) What do you mean by work. Give two examples each of positive work done , negative work done and zero work done?
B) what is the work to be done to increase the velocity of a car from 18 km/h to 90 km/h. The mass of car is 2000 kg.
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2
Answer:
Initial velocity u=30 km/h=30×
18
5
=
3
25
m/s
Final velocity v=60 km/h=60×
18
5
=
3
50
m/s
Mass m=1500 kg
Work done W=
2
1
mv
2
−
2
1
mu
2
⟹ W=
2
m
(v
2
−u
2
)=
2
1500
×((
3
50
)
2
−(
3
25
)
2
)=156187 J
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