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mizulyn

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1). Traffic lights are often timed so that if you travel at a certain constant speed, you can avoid all red lights. Discuss how the timing of the lights is determined, considering that the distance between them varies from one light to the next.

^ for this question, I said something about how timing is determined by the number of cars coming to the intersection vs. the cars passing the light, but I'm not sure that that's the answer that they're looking for.

2). The average velocity for a trip has a positive value. Is it possible for the instantaneous velocity at any point during the trip to have a negative value?

3). A ball is dropped from rest from the top of a building and strikes the ground with a speed of v. From ground level, a second ball is thrown straight upward at the same instant that the first ball is dropped. The initial speed of the second ball is v0 = v, the same speed with which the first ball will eventually strike the ground. Ignoring air resistance, decide whether the balls cross paths at half the height of the building, above the halfway point, or below the halfway point.

4). The muzzle velocity of a gun is the velocity of the bullet when it leaves the barrel. The muzzle velocity of one rifle with a short barrel is greater than the muzzle velocity of another rifle that has a longer barrel. In which rifle is the acceleration of the bullet larger?"

Thank you very much for any help!