The student engineer of a campus radio station wishes to verify the effectiveness of the lightning rod on the antenna mast (Fig. P27.49). The unknown resistance R x is between points C and E . Point E is a true ground, but it is inaccessible for direct measurement because this stratum is several meters below the Earth’s surface. Two identical rods are driven into the ground at A and B , introducing an unknown resistance R y . The procedure is as follows. Measure resistance R 1 between points A and B , then connect A and B with a heavy conducting wire and measure resistance R 2 between points A and C . (a) Derive an equation for R x in terms of the observable resistances, R 1 , and R 2 . (b) A satisfactory ground resistance would R x < 2.00 Ω. Is the grounding of the station adequate if measurements give R 1 = 13.0 Ω and R 2 = 6.00 Ω? Explain. Figure P27.49
The student engineer of a campus radio station wishes to verify the effectiveness of the lightning rod on the antenna mast (Fig. P27.49). The unknown resistance R x is between points C and E . Point E is a true ground, but it is inaccessible for direct measurement because this stratum is several meters below the Earth’s surface. Two identical rods are driven into the ground at A and B , introducing an unknown resistance R y . The procedure is as follows. Measure resistance R 1 between points A and B , then connect A and B with a heavy conducting wire and measure resistance R 2 between points A and C . (a) Derive an equation for R x in terms of the observable resistances, R 1 , and R 2 . (b) A satisfactory ground resistance would R x < 2.00 Ω. Is the grounding of the station adequate if measurements give R 1 = 13.0 Ω and R 2 = 6.00 Ω? Explain. Figure P27.49
Solution Summary: The author explains the equation for R_x in terms of the observable resistances.
The student engineer of a campus radio station wishes to verify the effectiveness of the lightning rod on the antenna mast (Fig. P27.49). The unknown resistance Rx is between points C and E. Point E is a true ground, but it is inaccessible for direct measurement because this stratum is several meters below the Earth’s surface. Two identical rods are driven into the ground at A and B, introducing an unknown resistance Ry. The procedure is as follows. Measure resistance R1 between points A and B, then connect A and B with a heavy conducting wire and measure resistance R2 between points A and C. (a) Derive an equation for Rx in terms of the observable resistances, R1, and R2. (b) A satisfactory ground resistance would Rx < 2.00 Ω. Is the grounding of the station adequate if measurements give R1 = 13.0 Ω and R2 = 6.00 Ω? Explain.
4.4 A man is dragging a trunk up the
loading ramp of a mover's truck. The
ramp has a slope angle of 20.0°, and
the man pulls upward with a force F
whose direction makes an angle of 30.0°
75.0°
with the ramp (Fig. E4.4). (a) How large a force F is necessary for the
component Fx parallel to the ramp to be 90.0 N? (b) How large will the
component Fy perpendicular to the ramp be then?
Figure E4.4
30.0
20.0°
1.
*
A projectile is shot from a launcher at an angle e, with an initial velocity
magnitude v., from a point even with a tabletop. The projectile lands on the tabletop
a horizontal distance R (the "range") away from where it left the launcher. Set this
up as a formal problem, and solve for vo (i.e., determine an expression for Vo in
terms of only R, 0., and g). Your final equation will be called Equation 1.
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