Electrostatics Question 462

Question: An electron moving with the speed 5×106 per sec is shooted parallel to the electric field of intensity 1×103N/C . Field is responsible for the retardation of motion of electron. Now evaluate the distance travelled by the electron before coming to rest for an instant (mass of e=9×1031Kg. charge =1.6×1019C) [MP PMT 2003]

Options:

A) 7 m

B) 0.7 mm

C) 7 cm

D) 0.7 cm

Show Answer

Answer:

Correct Answer: C

Solution:

Electric force qE=ma

therefore a=QEm

a=1.6×1019×1×1039×1031=1.69×1015

u=5×106 and v=0From v2=u22as

therefore s=u22aDistance s=(5×106)2×92×1.6×1015

=7cm.(approx)



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