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# A machine gun is attached to a railroad flatcar that rolls with negligible friction. If the railroad ...

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 A machine gun is attached to a railroad flatcar that rolls with negligible friction. If the railroad ... A machine gun is attached to a railroad flatcar that rolls with negligible friction. If the railroad car has a mass of 6.25  104 kg, how many bullets of mass 25 g would have to be fired at 250 m/s off the back to give the railroad car a forward velocity of 0.3 m/s?  a. 400  c. 3000  b. 2000  d. 5000[Ques. 2] A proton (+1.6  10-19 C) moves 10 cm on a path in the direction opposite to a uniform electric field of strength 3.0 N/C. How much work is done on the proton by the electrical field?  a. 4.8  10-20 J  c. zero  b. 1.6  10-20 J  d. -4.8  10-20 J[Ques. 3] A cannon of mass 1500 kg fires a 10-kg shell with a velocity of 200 m/s at an angle of 30 above the horizontal. Find the recoil velocity of the cannon across the level ground.  a. 1.15 m/s  c. 2.41 m/s  b. 0.94 m/s  d. 1.94 m/s[Ques. 4] An electron (charge -1.6  10-19 C) moves on a path perpendicular to the direction of a uniform electric field of strength 3.0 N/C. How much work is done on the electron as it moves 20 cm?  a. 1.6  10-20 J  c. 4.8  10-20 J  b. -4.8  10-20 J  d. zero[Ques. 5] Two particles collide, one of them initially being at rest. Is it possible for both particles to be at rest after the collision?  a. If the collision is perfectly inelastic, then this happens.  b. If the collision is elastic, then this happens.  c. This can happen sometimes if the more massive particle was at rest.  d. No.[Ques. 6] An electron and a proton are each released from rest in the same uniform electric field. The electron moves a distance delectron and the proton moves a distance dproton as each particle's kinetic energy increases by 1.6 eV. How do delectron and dproton compare?  a. delectron > dproton  b. delectron = dproton  c. delectron < dproton  d. The answer depends on the direction of the electric field.[Ques. 7] Two masses collide and stick together. Before the collision, one of the masses was at rest. Is there a situation in which the kinetic energy is conserved in such a collision?  a. Yes, if the less massive particle is the one initially at rest.  b. Yes, if the more massive particle is the one initially at rest.  c. Yes, if the two particles have the same mass.  d. No, kinetic energy is always lost is such a collision.[Ques. 8] Case 1: An electron is released from rest in a uniform electric field. Case 2: A proton is released from rest in a uniform electric field of the same magnitude as in case 1 . How does the electric potential energy of the charge-field system behave in these cases?  a. In case 1 the potential energy increases, but in case 2 it decreases.  b. In both cases, the potential energy increases.  c. In case 1 the potential energy decreases, but in case 2 it increases.  d. In both cases, the potential energy decreases.[Ques. 9] In a completely inelastic collision between two objects where the mass of one is double that of the other, which of the following statements is always true?  a. The larger mass will always lose kinetic energy.  b. The smaller mass will always gain kinetic energy.  c. The momentum of the smaller mass will have a larger magnitude change than that of the larger mass.  d. Not even one of the above statements is true.[Ques. 10] A proton consists of 3 quarks, two with charge +2e/3 and one with charge e/3 . Of the following, which is closest to the approximate potential energy of the arrangement of the two positive quarks if they are separated by 1015 m?  a. 1 MeV  c. 1012 MeV  b. 1019 MeV  d. 100 MeV Read 160 times 2 Replies
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datstragicbrodatstragicbro
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 2.   A machine gun is attached to a railroad flatcar that rolls with negligible friction. If the railroad car has a mass of 6.25×104 kg, how many bullets of mass 25 g would have to be fired at 250 m/s off the back to give the railroad car a forward velocity of 0.5 m/s?
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