whereas the bar magnet does not move (fig. 6.42) – Discussion Forum

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Kriti

Asked: September 17, 2026In: Class 9 Science

When the pole of a bar magnet is brought close to a magnetic compass, the bar magnet and the compass needle (which is also a magnet) exert a magnetic force on each other. As per Newton’s third law of motion, both the forces are equal in magnitude and opposite in direction. However, the compass needle moves, whereas the bar magnet does not move (Fig. 6.42). Explain why.

Both experience equal magnetic forces by Newton’s third law. The light compass needle pivots freely with negligible friction, whereas the much heavier bar magnet has high inertia and is held stationary by static friction with the surface.