A sort of \"projectile launcher\" is shown in . A large current moves in a close

Question

A sort of "projectile launcher" is shown in . A large current moves in a closed loop composed of fixed rails, a power supply, and a very light, almost frictionless bar (pale green) touching the rails.
A magnetic field is perpendicular to the plane of the circuit.Part AIf the bar has a length = 30 cm , a mass of 1.1 g , and is placed in a field of 2.2 T , what constant current flow is needed to accelerate the bar from rest to 30 m/s in a distance of 0.60 m ?

Express your answer to two significant figures and include the appropriate units.

Explanation / Answer

At firstly we find the acceleration of the bar using kinematices equations

v^2-u^2=2ad

30^2-0^2=2*a*0.6

900/1.2=a

the acceleration a=750 m/s^2

the force applied on the bar F=ma=1.1*10^-3*750=0.825 N

basing on lorentz principle

F=BiL

0.825=2.2*i*0.30

0.825=0.66*i

therefore the current i=1.25 A

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