Question

1. you pull a sled a distance of 100 m the force of friction opposing you is 20 n in the opposite direction. how much work did you do?

Explanation:

Step1: Recall work - formula

The work - done formula is $W = F\times d\times\cos\theta$, where $F$ is the force, $d$ is the displacement, and $\theta$ is the angle between the force and the displacement. Here, we want to find the work done by the person pulling the sled. The force applied by the person overcomes the frictional force. We assume the force applied by the person is in the direction of the displacement, and the frictional force is in the opposite direction. The force applied by the person $F$ (to move the sled against friction) has the same magnitude as the frictional force when the sled is moving at a constant speed. So $F = 20\ N$ (magnitude), $d=100\ m$, and $\theta = 0^{\circ}$ (since the force applied and the displacement are in the same direction), and $\cos\theta=\cos0^{\circ}=1$.

Step2: Calculate work

Substitute the values into the work - formula: $W = F\times d\times\cos\theta$.
$W=20\ N\times100\ m\times1$
$W = 2000\ J$

Answer:

$2000\ J$