An engine exerts a force 
and moves with velocity 
. The power of the engine (in watt) is:
Text Solution
Verified by ExpertsThe correct answer is:
A
Power is equal to the scalar product of force with velocity.
Power of the engine,
P = 
... (i)
Given
Thus, after substituting for 
and 
in equation (i), it becomes,
P = 
. 
= (20 × 6) 
= 120 – 60 – 15
= 45
Note: In the simplification for power, the dot product of a unit vector with same unit vector gives 1.
So, in above simplification second type of dot product are not shown.
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