1.

An electron moving with the speed 5 xx 10^6 m per second is shooted parallel to the electric field of intensity 1 xx 10^3 N/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 = 9.1 xx 10^(-31)kg)

Answer»

0.7 cm
0.7 mm
7 m
7 cm

Solution :Electric flux = NC force
`qE = mA`
`therefore a=(qE)/m =(1.6 XX 10^(-19) xx 10^(3))/(9.1 xx 10^(-31))`
`therefore a=0.1758 xx 10^(15) m//s^(2)`
Now equation of motion `v^(2) -v_(0)^(2) = 2ad`
`therefore d =(v^(2)-v_(0)^(2))/(2A)`, where `v=0, v_(0)=5 xx 10^(6) m//s`
`therefore =(25 xx 10^(12))/(3516 xx 10^(11)) = 0.00711 xx 10 = 0.0711` m
`=7.11 cm = 7 cm`


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