QuestionMarch 21, 2026

1. A girl exerts a 36 Newton horizontal force as she pulls a 52 Newton sled across a cement sidewalk at constant speed. What is the coefficient of kinetic friction between the sled and sidewalk? Ignore air resistance.

1. A girl exerts a 36 Newton horizontal force as she pulls a 52 Newton sled across a cement sidewalk at constant speed. What is the coefficient of kinetic friction between the sled and sidewalk? Ignore air resistance.
1. A girl exerts a 36 Newton horizontal force as she pulls a 52 Newton sled across a cement
sidewalk at constant speed. What is the coefficient of kinetic friction between the sled and
sidewalk? Ignore air resistance.

Solution
4.1(325 votes)

Answer

\mu_k \approx 0.69 Explanation 1. Identify forces and normal force Weight of sled W = 52\ \text{N}. Normal force N equals weight because motion is horizontal and no vertical acceleration. Thus N = 52\ \text{N}. 2. Apply constant speed condition At constant speed, pulling force equals friction: F_{\text{pull}} = F_{\text{friction}}. Given F_{\text{pull}} = 36\ \text{N}, so F_{\text{friction}} = 36\ \text{N}. 3. Use friction formula **F_{\text{friction}} = \mu_k N**. \mu_k = \frac{F_{\text{friction}}}{N} = \frac{36}{52}. 4. Calculate \mu_k \approx 0.692.

Explanation

1. Identify forces and normal force <br /> Weight of sled $W = 52\ \text{N}$. Normal force $N$ equals weight because motion is horizontal and no vertical acceleration. Thus $N = 52\ \text{N}$. <br /><br />2. Apply constant speed condition <br /> At constant speed, pulling force equals friction: $F_{\text{pull}} = F_{\text{friction}}$. Given $F_{\text{pull}} = 36\ \text{N}$, so $F_{\text{friction}} = 36\ \text{N}$. <br /><br />3. Use friction formula <br /> **$F_{\text{friction}} = \mu_k N$**. <br />$\mu_k = \frac{F_{\text{friction}}}{N} = \frac{36}{52}$. <br /><br />4. Calculate <br /> $\mu_k \approx 0.692$.
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