Final answer:
To calculate the work done by friction, we find the normal force affecting the sled, apply the friction coefficient to obtain the friction force, and then multiply the friction force by the distance over which the sled is moved.
Step-by-step explanation:
The question involves a child pulling a sled with constant speed at an angle of 30° to the horizontal surface. We need to calculate the work done by the friction force when the sled is dragged for 100 m, given a friction coefficient of 0.25 and the sled's mass of 9.1 kg.
First, calculate the normal force, which equals the gravitational force minus the vertical component of the pulling force. The gravitational force is the product of mass (m) and acceleration due to gravity (g), Fg = mg. The vertical component of the pulling force is Fp,vertical = Fp sin(30°), where Fp is the pulling force. Since the sled is moving at constant speed, we know that the pulling force must counteract the friction, so Fp,horizontal = Friction Force. The friction force can be calculated using Fr = μN, where μ is the friction coefficient and N is the normal force.
To find the normal force, we calculate N = mg - Fp sin(30°). We don't have the value of Fp, but since the sled moves at a constant speed, we know that the horizontal component of the pulling force equals the friction force, thus Fp cos(30°) = Friction Force.
Finally, the work done by friction, Wfriction, is the product of the friction force and the distance (d) moved in the direction of the force, which is Wfriction = Fr × d. Simplifying the equations and substituting the values, we get the work done by friction on the sled.