Electrostatics Question 370

Question: A mass $ m=20g $ has a charge $ q=3.0mC $ . It moves with a velocity of $ 20m/s $ and enters a region of electric field of $ 80N/C $ in the same direction as the velocity of the mass. The velocity of the mass after 3 seconds in this region is

Options:

A) $ 80m/s $

B) $ 56m/s $

C) $ 44m/s $

D) $ 40m/s $

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Answer:

Correct Answer: B

Solution:

$ a=\frac{QE}{m}=\frac{3\times {{10}^{-3}}\times 80}{20\times {{10}^{-3}}}=12m/sec^{2} $

Hence v = u + at therefore v = 20 + 12x 3 = 56 m/s.



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