Class Management Help Homework 4 Begin Date: 2/16/2018 12:01:00 AM-Due Date: 3/2

Question

Class Management Help Homework 4 Begin Date: 2/16/2018 12:01:00 AM-Due Date: 3/2/2018 9.00:00 AM End Date: 5/12/2018 11:59.00 PM (10%) Problem 7: A contender in a winter sporting event pulls a 44 kg brick of ice in the positive horizontal direction with a cord over his shoulders over' a frozen lake as shown in the figure Assume the coefficients of static and kinetic friction are 25° Otheexpertta.com ed 50% Part (a) Calculate the minimum force F he must exert to get the brick sliding in newtons. 50% Part (b) What is its acceleration in m/s2 once it starts to move, if that force is maintained? > Grade Summary Deductions 0% Potential 100% sin0 cotan0 as atan0 acotan0 sinh0 coshO tanh cotanhot Submissions acosO per attempt) detailed view

Explanation / Answer

(a) Assuming is w/r/t horizontal, then
normal force Fn = mg - Fsin = 44kg * 9.8m/s² - Fsin25º = 431.2N - 0.4226F

At the threshold, the static friction force is equal to the horizontal component of the applied force:
µs*Fn = Fcos
0.1*(431N - 0.4226F) = Fcos25 = 0.9063F
43.12 N = 0.9486F
F = 45.46 N

(b) Fnet = Fcos - µk*(431N - 0.4226F)
Fnet = 45.46N*cos25 - 0.03(431N - 0.4226*45.46N) = 41.2 N
a = Fnet / m = 41.2N / 44kg = 0.936 m/s²

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