A lawn mower has a 6-horsepower engine (1 HP = 750 W). If the engine has an efficiency of 20%, and the throttle is such that the engine cycles 10 times a second, the heat that is expelled in one cycle is
a. 1 800 J
b. 2 000 J
c. 2 200 J
d. 2 400 J
e. 2 250 J
A
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Which of the Jovian planets has rings?
A. Saturn B. Uranus C. Neptune D. Jupiter E. All of these choices are correct.
A force of 5.0 N is applied to a 20-kg mass on a horizontal frictionless surface. As the speed of the mass increases at a constant acceleration, the power delivered to it by the force:
a. remains the same. b. increases. c. decreases. d. doubles every 4.0 seconds.
An object is placed in front of a thin lens. Which statements are correct in describing the image formed by the lens? (There could be more than one correct choice.)
A) If the lens is convex, the image will never be virtual. B) If the image is real, then it is also inverted. C) If the image is real, then it is also upright. D) If the lens is concave, the image must be virtual. E) If the lens is convex, the image must be real.
In an elastic collision between two bodies of equal mass, with body 2 initially at rest, body 1 moves off at angle ? relative to the direction of its initial velocity and body 2 at angle ?. The sine of the sum of ? and ?, sin(? + ?), is equal to
a. 0. b. 0.500. c. 0.707. d. 0.866. e. 1.00.