A clerk can lift containers a vertical distance of 1 m, or roll them up a 2-m-long ramp to the same elevation. With the ramp, the applied force needed is
A) half as much.
B) twice as much.
C) the same.
Answer: A
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A(n) ____ is a single conjecture that can be tested
a. hypothesis b. paradigm c. natural law d. model e. theory
A car of mass M, traveling with a velocity V, strikes a parked station wagon, whose mass is 2M. The bumpers lock together in this head-on inelastic collision. What fraction of the initial kinetic energy is lost in this collision?
A) 1/4 B) 1/9 C) 1/2 D) 2/3 E) 1/3
The magnitude of the Poynting vector of a planar electromagnetic wave has an average value of 0.939 W/m2
The wave is incident upon a rectangular area, 1.5 m by 2.0 m, at right angles. How much total electromagnetic energy falls on the area during 1.0 minute? (c = 3.0 x 108 m/s, ?0 = 4? × 10-7 T ? m/A, ?0 = 8.85 × 10-12 C2/N ? m2) A) 210 J B) 170 J C) 340 J D) 250 J E) 300 J
Three pith balls supported by insulating threads hang from a support. We know that ball X is positively charged. When ball X is brought near balls Y and Z without touching them, it attracts Y and repels Z. Since pith is an insulating material, we can conclude that
a. Y has a negative charge. b. Z has a negative charge. c. Y has a positive charge. d. Z has a positive charge. e. Z is neutral (has no net charge.)