One goal of the Russian space program is to illuminate dark northern cities with sunlight reflected to the Earth from a 200-m diameter mirrored surface in orbit. Several smaller prototypes have already been constructed and put into orbit. (a) Assume that sunlight with intensity 1 370 W/m2 falls on the mirror nearly perpendicularly and that the atmosphere of the Earth allows 74.6% of the energy of sunlight to pass though it in clear weather. What is the power received by a city when the space mirror is reflecting light to it? (b) The plan is for the reflected sunlight to cover a circle of diameter 8.00 km. What is the intensity of light (the average magnitude of the Poynting vector) received by the city? (c) This intensity is what percentage of the vertical component of sunlight at St. Petersburg in January, when the sun reaches an angle of 7.00° above the horizon at noon?
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Chapter 34 Solutions
EBK PHYSICS FOR SCIENTISTS AND ENGINEER
- A uniform circular disk of mass m = 24.0 g and radius r = 40.0 cm hangs vertically from a fixed, frictionless, horizontal hinge at a point on its circumference as shown in Figure P34.39a. A beam of electromagnetic radiation with intensity 10.0 MW/m2 is incident on the disk, in a direction perpendicular to its surface. The disk is perfectly absorbing, and the resulting radiation pressure makes the disk rotate. Assuming the radiation is always perpendicular to the surface of the disk, find the angle through which the disk rotates from the vertical as it reaches its new equilibrium position shown in Figure 34.39b. Figure 34.39arrow_forwardWhat is the intensity of an electromagnetic wave with a peak electric field strength of 125 Vim?arrow_forwardThe electric part of an electromagnetic wave is given by E(x, t) = 0.75 sin (0.30x t) V/m in SI units. a. What are the amplitudes Emax and Bmax? b. What are the angular wave number and the wavelength? c. What is the propagation velocity? d. What are the angular frequency, frequency, and period?arrow_forward
- A community plans to build a facility to convert solar radiation to electrical power. The community requires 2.60 MW of power, and the system to be installed has an efficiency of 30.0% (that is, 30.0% of the solar energy incident on the surface is converted to useful energy that can power the community). Assuming sunlight has a constant intensity of 1 200 W/m2, what must be the effective area of a perfectly absorbing surface used in such an installation?arrow_forwardA possible means of space flight is to place a perfectly reflecting aluminized sheet into orbit around the Earth and then use the light from the Sun to push this "solar sail." Suppose a sail of area A = 6.90 x 105 m2 and mass m = 5,000 kg is placed in orbit facing the Sun. Ignore all gravitational effects and assume a solar intensity of 1,370 W/m?. (a) What force (in N) is exerted on the sail? (Enter the magnitude.) (b) What is the sail's acceleration? (Enter the magnitude in um/s2.) |um/s? (c) Assuming the acceleration calculated in part (b) remains constant, find the time interval (in days) required for the sail to reach the Moon, 3.84 x 10° m away, starting from rest at the Earth. days (d) What If? If the solar sail were initially in Earth orbit at an altitude of 400 km, show that a sail of this mass density could not escape Earth's gravitational pull regardless of size. (Calculate the magnitude of the gravitational field in m/s².) m/s2 (e) What would the mass density (in kg/m2) of…arrow_forwardA possible means of space flight is to place a perfectly reflecting aluminized sheet into orbit around the Earth and then use the light from the Sun to push this "solar sail." Suppose a sail of area A = 5.20 ✕ 105 m2 and mass m = 6,800 kg is placed in orbit facing the Sun. Ignore all gravitational effects and assume a solar intensity of 1,370 W/m2. (d) What If? If the solar sail were initially in Earth orbit at an altitude of 300 km, show that a sail of this mass density could not escape Earth's gravitational pull regardless of size. (Calculate the magnitude of the gravitational field in m/s2.) m/s2 (e) What would the mass density (in kg/m2) of the solar sail have to be for the solar sail to attain the same initial acceleration as that in part (b)? kg/m2arrow_forward
- Sunlight reaches the ground with an intensity of about 1.0 kW/m2 . A sunbather has a body surface area of 0.8 m2 facing the sun while reclining on a beach chair on a clear day. (a) how much energy from direct sunlight reaches the sunbather’s skin per second? (b) What pressure does the sunlight exert if it is absorbed?arrow_forwardThe average intensity of sunlight on Earth’s surface is about 700 W/m2 . (a) Calculate the amount of energy that falls on a solar collector having an area of 0.500 m2 in 4.00 h . (b) What intensity would such sunlight have if concentrated by a magnifying glass onto an area 200 times smaller than its own?arrow_forwardNASA is giving serious consideration to the concept of solar sailing. A solar sailcraft uses a large, low-mass sail and the energy and momentum of sunlight for propulsion. (a) Should the sail be absorbing or reflective? Why? (b) The total power output of the sun is 3.9 x 1026 W. How large a sail is necessary to propel a 10,000 kg spacecraft against the gravitational force of the sun? Express your result in square kilometers. (c) Explain why your answer to part (b) is independent of the distance from the sun.arrow_forward
- A possible means of space flight is to place a perfectly reflecting aluminized sheet into orbit around the Earth and then use the light from the Sun to push this "solar sail." Suppose a sail of area A = 5.20 x 105 m² and mass m = 6,200 kg is placed in orbit facing the Sun. Ignore all gravitational effects and assume a solar intensity of 1,370 W/m². (a) What force (in N) is exerted on the sail? (Enter the magnitude.) N (b) What is the sail's acceleration? (Enter the magnitude in µm/s².) μm/s² (c) Assuming the acceleration calculated in part (b) remains constant, find the time interval (in days) required for the sail to reach the Moon, 3.84 x 108 m away, starting from rest at the Earth. days (d) What If? If the solar sail were initially in Earth orbit at an altitude of 340 km, show that a sail of this mass density could not escape Earth's gravitational pull regardless of size. (Calculate the magnitude of the gravitational field in m/s².) m/s² (e) What would the mass density (in kg/m²) of…arrow_forwardA possible means of space flight is to place a perfectly reflecting aluminized sheet into orbit around the Earth and then use the light from the Sun to push this "solar sail. Suppose a sail of area A 6.30 x 10 m² and mass m - 7,000 kg is placed in orbit facing the Sun. Ignore all gravitational effects and assume a solar intensity of 1,370 W/m² (a) What force (in N) is exerted on the sail? (Enter the magnitude) (b) What is the sail's acceleration? (Enter the magnitude in um/s².) m/s² (c) Assuming the acceleration calculated in part (b) remains constant, find the time interval (in days) required for the sail to reach the Moon, 3.84 x 10 m away, starting from rest at the Earth days (d) What If? If the solar sail were initially in Earth orbit at an altitude of 400 km, show that a sall of this mass density could not escape Earth's gravitational pull regardless of size. (Calculate the magnitude of the gravitational field in m/s².) m/s² (e) What would the mass density (in kg/m²) of the solar…arrow_forwardIn theory, pressure from the sun's radiation could propel a spacecraft outward away from the sun. For a spacecraft of mass = 1340 kg at the same distance from the sun as Earth (150 million km), how much area would a 100% reflecting "sail" need to have in order to balance the sun's force of gravity acting on the spacecraft? For reference, the sun's intensity just outside Earth's atmosphere is 1400 W/m² and the sun's mass is 1,99 x 1030 kg, and the universal gravitational constant G = 6.67 x 10-11 Nm²/kg². Convert your answer to square km (1 km² = 106 m²). A = km²arrow_forward
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