Compound Microscope: The eyepiece of a compound microscope has a focal length of 2.50 cm, and the objective has a focal length of 1.60 cm. The two lenses are separated by 14.0 cm. The microscope is used by a person with normal eyes, having a near point at 25 cm. What is the magnitude of the magnification of the microscope?
A. 72
B. 88
C. 180
D. 219
E. 115
Answer: A
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A simply supported laminated beam of length L 5 0.5 m and square cross section weighs 4.8 N. Three strips are glued together to form the beam, with the allowable shear stress in the glued joint equal to 0.3 MPa. Considering also the weight of the beam, the maximum load P that can be applied at L/3 from the left support is approximately:
(A) 240 N
(B) 360 N
(C) 434 N
(D) 510 N
A power transmission line 50. km long has a total resistance of 0.60 ?. A generator produces 100. V at 70. A
In order to reduce energy loss due to heating of the transmission line, the voltage is stepped up with a transformer with a turns ratio of 100:1. (a) What percentage of the original energy is lost when the transformer is used? (b) What percentage of the original energy would be lost if the transformer were not used?
The Schwarzschild radius of a black hole is that radial distance from the center of a sphere within which not even light can escape
It was first discovered mathematically by Schwarzschild in 1916 after Einstein published his general relativity theory. It can be calculated from a star's mass M as: R = 2GM/c2. Take the radius of both stars A and B as the Schwarzschild radius. If the mass of star A is twice as much as the mass of star B, the average density of star A, compared to star B will be A) the same. B) twice as much. C) half as much. D) four times as much. E) one-fourth as much.
Frank says that if you release the string when swinging a ball in a horizontal circle, the ball flies out in the radial direction defined by the string at the instant you release the ball. John says that it flies out along a tangent line perpendicular to the string, and that it then drops straight down to the ground. Which one, if either, is correct?
a. Frank, because the centrifugal force is no longer counteracted by the string. b. Frank, because balls naturally fly straight out. c. John, because there is no centrifugal force. d. John, because balls fall straight down when released. e. Neither, because although there is no centrifugal force, and the ball's velocity is tangent to the circle at the instant of release, the ball then follows a parabolic trajectory.