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Ch3-HW1-solutions - louey(cal2859 Ch3-HW1 florin(56930 This...

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louey (cal2859) – Ch3-HW1 – florin – (56930) 1 This print-out should have 23 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. Problem @22: calculate the difference in the magnitudes of the fields, not the forces. 001(part1of4)10.0points Each part of this problem will state an ex- ample of objects interacting via some force. Choose the fundamental interaction that is responsible in each case. A neutron outside a nucleus decays into a proton,electron,andantineutrino. 1. Gravitational 2. Strong 3. Weak correct 4. Electromagnetic Explanation: Notice the presence of an antineutrino in this decay. Neutrinos (and their antiparticle partners) only interact via the weak force, so this must be a weak interaction. 002(part2of4)10.0points Protons and neutrons attract each other in anucleus. 1. Weak 2. Strong correct 3. Electromagnetic 4. Gravitational Explanation: The force that holds the nucleus together must be strong enough to overcome the repul- sion between protons due to the electromag- netic force. This is a strong interaction. 003(part3of4)10.0points TheEarthpullsontheMoon. 1. Strong 2. Weak 3. Gravitational correct 4. Electromagnetic Explanation: This is a gravitational interaction, in which massive bodies attract each other. 004(part4of4)10.0points Protonsinanucleusrepeleachother. 1. Electromagnetic correct 2. Gravitational 3. Weak 4. Strong Explanation: This is an example of an electromagnetic in- teraction, in which particles with like charges repel. 005(part1of2)10.0points The mass of the Sun is 2 × 10 30 kg, and the mass of Mercury is 3 . 3 × 10 23 kg. The distance from the Sun to Mercury is 4 . 8 × 10 10 m. First, calculate the magnitude of the gravi- tational force exerted by the Sun on Mercury. Use G = 6 . 67 × 10 - 11 m 3 kg · s 2 . Correct answer: 1 . 91068 × 10 22 N. Explanation: The magnitude of the gravitational force between two objects is given by vextendsingle vextendsingle vextendsingle vector F gr vextendsingle vextendsingle vextendsingle = vextendsingle vextendsingle vextendsingle vextendsingle Gm 1 m 2 r 2 vextendsingle vextendsingle vextendsingle vextendsingle = Gm 1 m 2 r 2 . We just need to plug in the given constants to find the answer: vextendsingle vextendsingle vextendsingle vector F gr vextendsingle vextendsingle vextendsingle = Gm 1 m 2 r 2
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louey (cal2859) – Ch3-HW1 – florin – (56930) 2 = ( G )(2 × 10 30 kg)(3 . 3 × 10 23 kg) (4 . 8 × 10 10 m) 2 = 1 . 91068 × 10 22 N . where G = 6 . 67 × 10 - 11 m 3 kg · s 2 . 006(part2of2)10.0points Calculate the magnitude of the gravitational force exerted by Mercury on the Sun. Correct answer: 1 . 91068 × 10 22 N. Explanation: By Newton’s third law, and by simply look- ing at the formula for the gravitational force, it is clear that the force exerted by Mercury on the Sun will be the same as that exerted by the Sun on Mercury.
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