Collisions in Two Dimensions: A car heading north suddenly collides at an intersection with a truck of the same mass heading east. If they lock together and travel at 28 m/s at 15° north of east just after the collision, how fast was the car initially traveling?
A. 14 m/s
B. 7 m/s
C. 28 m/s
D. 11 m/s
Answer: A
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What is thought to be the reason that there are no small impact craters on Mars?
A) Like Venus, Mars' atmosphere is too thick and these meteorites do not survive to make impacts on the surface. B) The surface of Mars is too young to have impact craters. C) Due to the gravitational pull of Mars' moons, most small meteoroids are deflected and never make it to the surface. D) The wind blows small dust particles, eroding the surface of Mars, erasing small impact craters faster than they can form. E) None of the above. Mars has lots of small impact craters.
An aluminum tube (E 5 72 GPa) AB of circular cross section has a pinned support at the base and is pin-connected at the top to a horizontal beam supporting a load Q 5 600 kN. The outside diameter of the tube is 200 mm and the desired factor of safety with respect to Euler buckling is 3.0. The required thickness t of the tube is most nearly:
(A) 8 mm
(B) 10 mm
(C) 12 mm
(D) 14 mm
What does Hubble's law tell us?
A) The more distant a galaxy, the faster it is moving away from us. B) The faster a spiral galaxy's rotation speed, the more luminous it is. C) The longer the period of a Cepheid variable, the greater its luminosity. D) For every force, there is an equal and opposite reaction force.
Based on current understanding, what exactly is causing the expansion of the universe to accelerate?
A) WIMPs B) neutrinos C) white dwarf supernovae D) Gravity E) We don't know, but we call it "dark energy."