54. (a) When the proton is released, its energy is K + U = 4.0 eV + 3.0 eV (the latter value is inferred from the graph). This implies that if we draw a horizontal line at the 7.0 Volt “height” in the graph and find where it intersects the voltage plot, then we can determine the turning point. Interpolating in the region between 1.0 cm and 3.0 cm, we find the turning point is at roughly x = 1.7 cm. (b) There is no turning point towards the right, so the speed there is nonzero, and is given by energy conservation: v = 2(7.0 eV) m = 2(7.0 eV)(1.6 x 10-19 J/eV) 1.67 x 10-27 kg = 20 km/s. (c) The electric field at any point P is the (negative of the) slope of the voltage graph
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This note was uploaded on 12/13/2010 for the course PHYS 157 taught by Professor Ur during the Spring '10 term at NE Texas CC.