Chapter 8 - Potential Energy and Conservation of Energy - Problems - Page 206: 54a

$\Delta E_{th} = 153J$

$\Delta E_{th} = f_k \times d$ $\Delta E_{th} = (μ_kF_N) \times d$ $\Delta E_{th} = (μ_kmgcos\theta) \times d$ $\Delta E_{th} = (0.1\times 267\times 9.8 \times cos20^{\circ}) \times 6.1$ $\Delta E_{th} = 153J$