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Two particles, each having a mass m are placed at a separation d in a uniform magnetic field B as shown in they have opposite charges of equal magnitude q. at time t =0, the particles are projectd towards each other,each with a speed v. suppose the coulomb force between the charges is switched off. (a)Find the maximum value v_m ofthe projection speed so that the two particles do not collide. (b)What would be the minimum and maximum separation between the particles if v =v_m /2? (c) At whatinstant will a collision occur betweenthe particles if v = 2v_m ? (d) Suppose v =2v_m and the collision between the particles is completely inelastic. Describe the motion after the collision.

Answer»

Solution :The particles will not collide if
`d = r_(1) + r_(2)`
`rArr d = ((mV)/(qB) + (mV)/(qB) + (2mV)/(qB))`
`v= (qBd)/(2m)`
`d_(1) = r_(1)+r_(2) = 2r`
`rArr = (d)/(2)`(minimum distance)
Max distance ,
`d_(2) = + d + 2r = d + (d)/(2)= (3d)/(2)`
`( c ) V= 2V _(2) m`
`r_(1) = r_(2) = d `The are is `(1)/(6)`
`(d )V = 2V_(m)`
The particle will collide at point P . At point P , both the particle will have motion `m` in upward direction . Since the particle collide inelastically they stick together distance`i` between centers `= d`,
`sinsintheta = (i)/(2r)`velocity upward
`= v cos (90 - sin theta ) = (vi)/(2r)`
`(mv^(2) )/(r)= QVB`
` rArr r = (mV)/(qB)`
Using `(mu^(2) )/(r)= (qvB)/(2m)= V_(m)`
HENCE the COMBINE mass will movewith the velocity `V_(m)`


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