Act5_sol - 5.1 What Are the Four Fundamental Forces? a)...

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17 Period 5 Activity Sheet Solutions: Forces and Newton’s Laws 5.1 What Are the Four Fundamental Forces? a) Based on your class activities and your instructor’s explanation, give examples of each of the fundamental forces. 1) Gravitational Force An attractive force between all objects. The gravitational force causes objects to roll downhill, causes dropped objects to fall toward the Earth, and holds the Earth in an orbit around the Sun. Example: an unsupported object falls to the ground. 2) Electromagnetic Force An attractive force between particles of opposite charge, and a repulsive force between particles with like charge (both positive or both negative). The electromagnetic force holds atoms together and causes charged objects to attract or repel one another. Example: when the negatively charged styrofoam ring is repelled by the negatively charged rod, the ring floats above the rod. 3) Strong Nuclear Force An attractive force that holds protons and neutrons together in the nuclei of atoms. The strong force acts only when particles are close together. Example: all matter consisting of atoms. 4) Weak Nuclear Force The force responsible for radioactive decay of atomic nuclei, such as the decay that produces radon gas. Example: decay of radioactive samples. b) The space between an atomic nucleus and its electron cloud is so great that the majority of the volume of an atom is empty space. Since atoms are mostly empty space, explain in terms of fundamental forces why a solid object sitting on a table does not fall through the table. Electromagnetic forces between atoms lock atoms together to form a solid. In most solids, these forces are strong enough to prevent the solid from falling apart when subjected to a force. c) Group Discussion Question: Since all objects contain positive and negative electrical charges, shouldn’t we feel an electromagnetic force from every object we encounter? Explain why we do not.
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18 g M D M M G F rock planet rock = = 2 5.2 How Do Newton’s Laws of Motion Describe Forces? a) Newton’s First Law: Your instructor will demonstrate a metal cart on an air track, which minimizes the amount of friction between the cart and the metal track. 1) As the cart moves along the track, is there a net force acting on the cart? __ Since there is very little friction between the cart and the track, the net force is essentially zero. __ 2) Is a net force required to keep the cart moving at a constant speed? _ No _ Explain why or why not. According to Newton’s first law, a force must act on an object in motion to change the object’s speed or direction. Since the cart moves at a constant speed along the track, its acceleration is zero and no net force is required. b)
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This note was uploaded on 06/11/2011 for the course PHYSICS 103 taught by Professor Staff during the Spring '10 term at Ohio State.

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Act5_sol - 5.1 What Are the Four Fundamental Forces? a)...

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