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Can the nut of the axle of a bike be loosened with a hand why do we use a spanner for this purpose?
No, we cannot loosen the nut of the axel of a bike. Normally we use a spanner because a spanner increases the turning effect of the force which easily loosened the nut of the axle of a bike.
Women and children in the villages often carry pitchers with water on their heads how this is possible?
Women and children keep themselves upright when carrying pitchers on their heads. The pitcher has a heavy semi-spherical base. When it is tilted, its center of mass rises. It returns to its upright position at which its center of mass is at its lowest. That is why women and children in the villages often carry pitchers with water on their heads.
