2. Mark Watney is testing a crazy idea in Mars (see Fig.2). In order to get a free ride through Mars due to gravity, a team dig a straight tunnel from north pole to the south pole. Let's assume Mars is a perfect sphere with mass of 6.42×1023 kg and radius of 3400 km and neglect the air resistance. How long will a round trip take for Mark Watney when he jumps into the tunnel with zero initial velocity? The gravitational constant G = 6.67×10-11 Nm²/kg². (A) 10 hours (B) 400 minutes (C) 23 hours (D) 100 minutes

10. Figure 5 illustrates a particle accelerator called cyclotron. It is composed of two hollow metal semicircular containers D1 and D2, and a source of charged particle, e.g., proton, at the center. A high frequency alternating electric potential is applied to D1 and D2, which will generate an alternating electric field in the gap between D1 and D2. A uniform and static magnetic field B is applied vertically to bend the trajectory of a charged particles in a cyclotron. In order to accelerate the charged particle, at each time when the particle passes the gap, one has to change the direction of . Please calculate the angular frequency of the alternating electric voltage in terms of particle mass m, charge e, magnitude of the static magnetic field . (A)(B)(C)(D)

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