An umbrella tends to move upwards on a windy day principally because
A) trapped air under the umbrella, warms, and rises.
B) buoyancy increases with increasing wind speed.
C) air pressure is reduced over the curved top surface.
D) all of the above
Answer: C
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Photoelectric Effect: When a metal is illuminated by light, photoelectrons are observed provided that the wavelength of the light is less than 520 nm. What is the metal's work function? (c = 3.00 × 108 m/s, h = 6.626 × 10-34 J ? s, 1 eV = 1.60 × 10-19 J)
A. 2.4 eV B. 2.6 eV C. 2.8 eV D. 3.0 eV
An airplane flies horizontally with a speed of 300 m/s at an altitude of 400 m. Assume that the ground is level. At what horizontal distance from a target must the pilot release a bomb so as to hit the target?
A. 3.0 km B. 2.4 km C. 3.3 km D. 2.7 km E. 1.7 km
Large curved cooling towers can often be seen at
A) steam-electric power plants. B) nuclear power plants. C) Both of the above. D) hydro-electric plants. E) All of the above.
The efficiency of an engine can be defined as the
A. ratio of work done to energy input. B. ratio of work done to energy exhausted. C. ratio of heat exhausted to heat intake. D. total amount of work performed.