Question

1. a 10 kg crate is sitting on a wooden desk. the coefficient of kinetic friction ($\mu_{k}=0.18$) and coefficient of static friction ($\mu_{s}=0.3$). if a force of 30 n is used to push the crate, would the crate begin to move? explain.

Explanation:

Step1: 計算最大靜摩擦力

最大靜摩擦力公式為 \(F_{s}=\mu_{s}N\)，物體在水平桌面，\(N = mg\)（\(m = 10\space kg\)，\(g = 9.8\space m/s^{2}\)），則 \(N=10\times9.8 = 98\space N\)。
代入 \(\mu_{s}=0.3\)，可得 \(F_{s}=0.3\times98=29.4\space N\)。

Step2: 比較推力與最大靜摩擦力

已知推力 \(F = 30\space N\)，因為 \(F>F_{s}\)（\(30>29.4\)）。

Answer:

The crate would begin to move. Because the applied force \(30\space N\) is greater than the maximum static - friction force \(29.4\space N\).