When a bicyclist coasts straight down a hill at a constant speed, several forces are at play. The primary forces include gravitational force, normal force, and air resistance. Given that the mass of the rider and bicycle is 60.0 kg and the hill is inclined at 11.0 degrees, we need to consider the components of the gravitational force acting along the slope and opposing the motion, which is caused by air resistance.
The gravitational force can be broken down into two components: one acting parallel to the slope of the hill and the other acting perpendicular to it. The parallel component is what pulls the cyclist down the hill, while the perpendicular component influences the normal force.
The fact that the cyclist is moving at a constant speed implies that the forces are balanced. This means that the force of gravity acting down the slope is equal to the force of air resistance opposing the motion. Therefore, since no net force acts on the cyclist, their speed remains unchanged.
It is important to note that while the cyclist is coasting down at a constant speed, they are not accelerating, despite being on an incline. The angle of the hill (11.0 degrees) influences the gravitational force component, but as long as air resistance matches this pull, the rider will maintain that constant speed.