physics_ch2homework

# physics_ch2homework - Chapter 2 Homework 1 A rocket...

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Chapter 2 Homework 1. A rocket carrying a satellite is accelerating straight up from the earth’s surface. At 1.15 s after liftoff, the rocket clears the top of its launch platform, 63 m above the ground. After an additional 4.75 s, it is 1.00 km above the ground. Calculate the magnitude of the average velocity of the rocket for: (a) the 4.75-s part of its flight - = vav x ∆x∆t = - . 1000 m 63m4 75 s = / 197 m s (b) the first 5.90 s of its flight. - = - . vav x 1000 m 0 m5 90 s = / 169 m s 2. In an experiment, a shearwater (a seabird) was taken from its nest, flown 5150 km away, and released. The bird found its way back to its nest 13.5 days after release. If we place the origin in the nest and extend the +x-axis to the release point, what was the bird’s average velocity in m/s for: (a) the return flight - = - . vav x 0 km 5150 km13 5 days 1000 m1 km1 day24 hours1 hour60 mins1 min60 s = - . / 4 42 m s (b) the whole episode, from leaving the nest to returning - = - vav x 0 km 0 km∆t 1000 m1 km1 day24 hours1 hour60 mins1 min60 s = / 0 m s 4. Starting from a pillar, you run 200 m east (the +x-direction) at an average speed of 5.0 m/s, and then run 280 m west at an average speed of 4.0 m/s to a post. Calculate: (a) your average speed from pillar to post = . / + . / = t 200 m5 0 m s 280 m4 0 m s 110 s - = speedav x dt = + 200 m 280 m110 s = . / 4 36 m s (b) your average velocity from pillar to post - = - vav x 200 m 80 m110 s = - . / 0 727 m s Page | 1 1.19.11

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9. A car is stopped at a traffic light. It then travels along a straight road so that its distance from the light is given by = - xt bt2 ct3 where = . / b 2 40 m s2 and = . / c 0 120 m s3 . (a) Calculate the average velocity of the car for the time interval t = 0 to t = 10.0 s. = . - . = x0 2 40ms20 s2 0 120ms30 s3 0 m . = . . - . . = x10 0 2 40ms210 0 s2 0 120ms310 0 s3 120 m - = - . - = . / vav x 120 m 0 m10 0 s 0 s 12 0 m s (b) Calculate the instantaneous velocity of the car at t = 0, t = 5.0 s, and t = 10.0 s = - xt bt2 ct3 = = - vxt dxdt 2bt 3ct2 = . - . = / vx0 s 22 40ms20 s 30 120ms30 s2 0 m s . = . . - . . = . / vx5 0 s 22 40ms25 0 s 30 120ms35 0 s2 15 0 m s . = . . - . . = . / vx10 0 s 22 40ms210 0 s 30 120ms310 0 s2 12 0 m s (c) How long after starting from rest is the car again at rest? = - 0 2bt 3ct2 = 2bt 3ct2 = = . . = . t 2b3c 22 40ms230 120ms3 13 3 s 10. A physics professor leaver her house and walks along the sidewalk toward campus. After 5 minutes it starts to rain and she returns home. Her distance from her house as a function of time is shown. At which of the labeled points is her velocity (a) zero? point IV (b) constant and positive? point I (c) constant and negative? point V Page | 2 1.15.11
point II

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## This note was uploaded on 03/26/2011 for the course PHY 210 taught by Professor Mcdemus during the Spring '11 term at Lehigh Carbon CC.

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physics_ch2homework - Chapter 2 Homework 1 A rocket...

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