A freight train consists of an engine and several identical cars on a level track. Which of the following statements is true?
A. if the train is moving at constant speed, the engine must be pulling with a force greater than the train's weight
B. if the train is moving at constant speed, the engine's pull on the first car must exceed that car's backward pull on the engine
C. if the train is coasting, its inertia makes it slow down and eventually stop
D. if the train is moving at constant speed the engine's pull must be equal to the friction
D. if the train is moving at constant speed the engine's pull must be equal to the friction
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The first to be credited with the idea that energy was quantized was
A) Max Planck. B) Albert Einstein. C) both Planck and Einstein at about the same time.
The most abundant gas making up the Sun's composition is _______________
Fill in the blank(s) with correct word
Energy Conservation With Conservative Forces: A prankster drops a water balloon from the top of a building. If the balloon is traveling at 29.1 m/s when it strikes a window ledge that is 1.5 m above the ground, how tall is the building? Neglect air resistance.
A. 45 m B. 43 m C. 46 m D. 47 m
A spaceship traveling at constant speed away from the Sun crosses the orbit of Earth and later crosses the orbit of Mars
What is the distance between these two events in the spaceship frame of reference? The radius of Earth's orbit is 150 × 109 m and that of Mars is 228 × 109 m.