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092110physhw

# 092110physhw - f = V i at V f = 0.00 m/s(9.80 m/s 2(4.0 s V...

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David Kim Physics Period 9 9/21/10 HW #4 Pg. 74 # 42-44 42. A construction worker accidentally drops a brick from a high scaffold. a. What is the velocity of the brick after 4.0 s? b. How far does the brick fall during this time? a. V f = V i +at V f = 0.00 m/s + (-9.80 m/s 2 )(4.0 s) V f = -39.2 m/s b. d f = d i + v i t + ½at 2 d f = 0.00 m + (0.00 m/s)(4.0 s) + ½(-9.80 m/s 2 )(4.0 s) 2 d f = -19.6 m 43. Suppose for the previous problem you choose your coordinate system so that the opposite direction is positive? a. V
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Unformatted text preview: f = V i +at V f = 0.00 m/s + (9.80 m/s 2 )(4.0 s) V f = 39.2 m/s b. d f = d i + v i t + ½at 2 d f = 0.00 m + (0.00 m/s)(4.0 s) + ½(9.80 m/s 2 )(4.0 s) 2 d f = 19.6 m 44. A student drops a ball from a window 3.5 m above the sidewalk. How fast it is moving when it hits the sidewalk? d f = d i + v i t + ½at 2 3.5 m = 0.00 m + (0.00 m/s)(t) +½(9.80 m/s 2 )t 2 t 2 = 5/7 s 2 V f = V i +at V f = 0.00 m/s + (9.80 m/s 2 )(√5/7 s) V f = 8.28 m/s...
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