hw01soln - Phys ic s 1 4 4 Va is hna v S pr ing 2 0 1 0 Ho...

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Phys ic s 1 4 4 – Vaishnav Spring 2010 Ho w T hing s Wo r k Ho m e wo r k Se t # 1 Solutions Problem 1: a) Chapt e r 1 , Exercise 2 (p. 38): As you jump across a small stre am, doe s a horizontal force keep you moving forward? What is that force ? No—once you are in the air, no force acts on you. You are carried forward by inertia. b) Chapt e r 1 , Exercise 4 (p. 38): Why doe s tapping your toothbrush on the sink dry it off? Water is slipper y and is not held to the toothbrush by much friction. When the toothbrush stops, very little force acts on the water, which keeps moving forward due to inertia. c) Chapt e r 1 , Exercise 6 (p. 38): An unse atbe lte d drive r can be injure d by the ste e ring wheel during a head-on collision. Why does the driver hit the steering wheel when the car comes to a stop? Before the crash, car, seat, and driver are all moving forward. A force acts on the car and stops it. Howev er i f the driver is not wear ing a seat belt, he or she is not attached to the car, which then exer ts no di r ec t force on the driver ’s upper body. So due t o i t s i ner t i a, the driver ’s upper body keeps moving forward, even when the car has stopped. Problem 2 : As part of Lab #1 , e ach pe rson in the class counte d the total numbe r of M&M’ s in h is o r h e r o w n b a g . There were 23 bags counted, and the individual results follow: 56, 56, 58, 60, 57, 59, 57, 55, 59, 59, 55, 58, 58, 59, 60, 61, 58, 58, 58, 57, 57, 60, 59 . a) Calc ulat e t he e xpe rime nt al me an, t he s t andard de viat io n, and t he s t andard de viat io n o f the mean. You don’t have to show all your calculations here, but you do need to explain (with words or with equations) how you calculated each of the requested quantities. Since we’re talking about numbers of M&M’s, round your final answers to the tenths place (i.e you would round 2.413 to 2.4). Usi ng the same techni ques as i n the l ab, I cal cul ated the exper i mental mean by addi ng up al l the val ues and then dividing by the total number ( in this case, 2 3 ) to obtain 5 8 . To calculate the standar d devi at i on, I t ook eac h of the individual values, subtracted the experimental mean from them, and took the aver age of those number s. Then, I took the squar e r oot of the aver age to obtain 1 .5 6 , which I r ounded to 1.6 following the instructions. To get the standard
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This note was uploaded on 03/27/2011 for the course PHYS 144 taught by Professor ? during the Spring '06 term at Bucknell.

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hw01soln - Phys ic s 1 4 4 Va is hna v S pr ing 2 0 1 0 Ho...

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