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Exam1_2011_Winter_Solutions

# Exam1_2011_Winter_Solutions - Physics 140 Winter 2011 First...

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Physics 140, Winter 2011, Midterm 1 Problem 1: The value of is: A. zero B. +1 C. –1 D. 3 E. Answer C. Problem 2: Figure shows a 10 kg mass suspended from two spring scales, each of which has negligible weight. Thus, Each scale will measure the tension (divided by g ). The tension is 10 g in both. Answer E. Problem 3: A child standing on a bridge throws a rock straight down. The rock leaves the child’s hand at t = 0. Which of the graphs best represents the velocity of the stone as a function of time? Neglect air resistance. 10k g 0 A v y t 0 B v y t 0 C v y t 0 D v y t 0 E v y t
If we take up positive then . The initial velocity is down so it’s negative too. A line with a negative intercept and a slope of – g . Answer C. Problem 4: Three boxes with mass m 1 = 1kg, m 2 = 2kg, and m 3 = 3kg are hanging from strings as shown in figure. You are pulling the top string with the force of 100N. What is the tension T 12 in the string connecting boxes m 1 and m 2 ? Treating all three objects together and just grouping 2 and 3 give the following FBDs: Calling up positive Newton’s 2 nd Law gives for all three and for the bottom two. Solve for a in the first equation and plug into the 2 nd

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Exam1_2011_Winter_Solutions - Physics 140 Winter 2011 First...

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