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Physics Acceleration

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Chapter 6. Uniform Acceleration

Problems:
Speed and Velocity
6-1. A car travels a distance of 86 km at an average speed of 8 m/s. How many hours were required for the trip?
[pic] [pic] t = 2.99 h
6-2. Sound travels at an average speed of 340 m/s. Lightning from a distant thundercloud is seen almost immediately. If the sound of thunder reaches the ear 3 s later, how far away is the storm?
[pic] t = 58.8 ms
6-3. A small rocket leaves its pad and travels a distance of 40 m vertically upward before returning to the earth five seconds after it was launched. What was the average velocity for the trip?
[pic] v = 16.0 m/s
6-4. A car travels along a U-shaped curve for a distance of 400 m in 30 …show more content…

For Problem 6-17, what is the maximum displacement from the bottom and what is the velocity 4 s after leaving the bottom? (Maximum displacement occurs when vf = 0)
2as = vo2 - vf2; [pic]; s = +21.3 m vf = vo + at = 16 m/s = (-6 m/s2)(4 s); vf = - 8.00 m/s, down plane 6-19. A monorail train traveling at 80 km/h must be stopped in a distance of 40 m. What average acceleration is required and what is the stopping time? ( vo = 80 km/h = 22.2 m/s)
2as = vo2 - vf2; [pic]; a = -6.17 m/s2
[pic] ; t = 3.60 m/s

Gravity and Free-Falling Bodies
6-20. A ball is dropped from rest and falls for 5 s. What are its position and velocity? s = vot + ½at2; s = (0)(5 s) + ½(-9.8 m/s2)(5 s)2 ; s = -122.5 m vf = vo + at = 0 + (-9.8 m/s2)(5 s); v = -49.0 m/s

6-21. A rock is dropped from rest. When will its displacement be 18 m below the point of release? What is its velocity at that time? s = vot + ½at2; (-18 m) = (0)(t) + ½(-9.8 m/s2)t2 ; t = 1.92 s vf = vo + at = 0 + (-9.8 m/s2)(1.92 s); vf = -18.8 m/s

6-22. A woman drops a weight from the top of a bridge while a friend below measures the time to strike the water below. What is the height of the bridge if the time is 3 s? s = vot + ½at2 = (0) + ½(-9.8 m/s2)(3 s)2; s = -44.1 m

6-23. A brick is given an initial downward velocity of 6 m/s. What is its final velocity after falling a distance of 40 m?
2as = vo2 - vf2 ; [pic]; v = (28.6 m/s;

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