A sort of “projectile launcher” is shown in Fig. 20–71. A

Chapter 20, Problem 87GP

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A sort of “projectile launcher” is shown in Fig. 20–71. 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. If the bar has a length  \(I=28 \mathrm{~cm}\), a mass of 1.5 g, and is placed in a field of 1.7 T, what constant current flow is needed to accelerate the bar from rest to \(28 \mathrm{~m} / \mathrm{s}\) in a distance of 1.0 m? In what direction must the magnetic field point

FIGURE 20–71 Problem 87.

Equation transcription:

Text transcription:

I=28{~cm}

28{~m} /{s}