A 79.5 kg firefighter slides down a pole while a constant frictional force of 30

Question

A 79.5 kg firefighter slides down a pole while a constant frictional force of 300 N her motion. A horizontal 20.0 kg platform is supported by a spring at the bottom of the pole to cushion the fall. The firefighter starts from rest 4.50 m above the platform, and the spring constant is 4000 N/m. Find the firefighter's speed just before she collides with the platform. differs from the correct answer by more than 10%. Double check your calculations, m/s Find the maximum distance the spring is compressed. (Assume the frictional force acts during the entire motion.) Note, WebAssign has you solve this problem as if the platform was not compressed before the collision. m

Explanation / Answer

m = 79.5 Kg , F = 300 N

acceleration due to friction force = F / m = 300 / 79.5 = 3.77 m/s2

Effective acceleration on firefighter = 9.8 - 3.77 = 6.03 m/s2

v2 - u2 = 2 a s

v = sqrt (2 * 6.03 * 4.50) = 7.37 m/s

b) From conservation of energy 1/2 m v2 = 1/2 K x2

79.5 * 7.372 = 4000 * x2

x = 1.04 m

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