Which of the following statements are true? (A) A force can act on an object with or without being in contact with it (B) Earth's molten metallic core is the origin of the magnetic field (C) Gravitational forces is one of the strongest forces (D) Nuclear forces are weakest of fundamental forces
(A) and (B)
Statement (A) is true because forces can be either contact forces, such as friction or the push of a hand, or non-contact (action-at-a-distance) forces, such as gravitational and magnetic forces.
Statement (B) is true because the motion of molten, electrically conducting material in Earth's outer core generates electric currents that produce Earth's magnetic field, a process known as the geodynamo.
Statement (C) is false because among the four fundamental forces of nature, the gravitational force is actually the weakest, not one of the strongest.
Statement (D) is false because the strong nuclear force is the strongest of the four fundamental forces, not the weakest.
Hence, statements (A) and (B) are the true statements.
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