Pad 3:55 AM 3196 edugen.wileyplus.com FULL SCREEN PRINTER VERSION BACK NEXT ASSI

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Pad 3:55 AM 3196 edugen.wileyplus.com FULL SCREEN PRINTER VERSION BACK NEXT ASSIGNMENT RESOURCES Chapter 10, Problem 14 HW10 PHYS2001 Fall 2017 A 10.8-kg block rests on a horizontal table and is attached to one end of a massless, horizontal spring. By pulling horizontally on the other end of the spring, someone causes the block to accelerate uniformly and reach a speed of 4.75 m/s in 0.559 s. In the process, the spring is stretched by 0.152 m. The block is then pulled at a constant speed of 4.75 m/s, during which time the spring is stretched by only 0.0745 m. Find (a) the spring constant of the spring and (b) the coefficient of kinetic friction between the block and the table Focus on Concepts, Question 14 Chapter GO Cha Chapter Chapter Chapter 10, Problem (a) Number Units Proble (b) Number Units oblem LINK TO TEXT hapter 10, Problem 14 Question Attempts: Unlimited SAVE FOR LATER SUBMIT ANSWER GO Chapter Chapter 10, Problem Problem 43 oblem 45 hapter GO Chapter 10, Problem Review Score Review Results by Study Objective

Explanation / Answer

The block's acceleration is
a = 4.75 m/s / 0.559s = 8.5 m/s^2

So the net accelerating force on the block is
fa = m*a = 10.8 * 8.5 N = 91.8 N

The friction force ff also stretches the spring at the other end and is the ONLY stretching force at constant speed:
so ff = 0.0745m * k

(a) So the total stretching force is
fa + ff = 91.8 + 0.0745*k = k*x = 0.152*k

so k = 91.8 / (0.152 - 0.0745) N/m = 1185 N/m

(b) ff = k*m*g = 0.0745 * 1185 N = 88.3N
so the coeff of kinetic friction is

k = 88.3 / (10.8*9.8) = 0.834

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