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Work, Power and Energy

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Question : 11
Total: 30
A body constrained to move along the z-axis of a coordinate system is subject to a constant force F given by
F=−
^
i
+2
^
j
+3
^
k
N
where
^
i
,
^
j
,
^
k
 are unit vectors along the x, y and z-axis of the system respectively. What is the work done by this force in moving the body a distance of 4 m along the z-axis?
Solution:  
Given that
→
F
=(−
^
i
+2
^
j
+3
^
k
)N,
→
d
=4
^
k

W=
→
F
.
→
d
 =(−
^
i
+2
^
j
+3
^
k
).(4
^
k
)
=12
^
k
.
^
k
=12J
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