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  1. A body of mass 1 kg begins to move under the action of a time dependent force F = (2tî + 3t2ĵ) N, where î and ĵ are unit vectors alogn x and y axis. What power will be developed by the force at the time t?​​
    1. ​(2t2 + 3t3)W ​
    2. ​(2t2 + 4t4)W ​
    3. ​(2t3 + 3t4) W
    4. (2t3 + 3t5)W
Correct Option: D

Given force F = 2tî + 3t2
According to Newton's second law of motion,

m
dv
= 2tî + 3t2ĵ (m = 1 kg)
dt


⇒ v = t2î + t3
Power P = F . v = (2tî + 3t2ĵ) . (t2î + t3ĵ)
= (2t3 + 3t5)W



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