Final Answer:
A car travels down a straight road that leads over hills and through valleys. On one particular stretch of road, the car encounters a hill that can reduce its speed.
Step-by-step explanation:
When a car encounters a hill, several factors come into play that can affect its speed. The primary force at play is gravity, which acts to pull the car downward. As the car ascends the hill, it has to overcome the gravitational force working against it. The force of gravity can be broken down into two components: one parallel to the incline of the hill (mg sinθ) and the other perpendicular to the incline (mg cosθ). Here, 'm' is the mass of the car, 'g' is the acceleration due to gravity, and 'θ' is the angle of the hill.
The component of gravity acting parallel to the incline acts as a resistance force, opposing the car's forward motion. This results in a decrease in the car's speed as it moves uphill. The steeper the incline (larger 'θ'), the greater the resistance force due to gravity, and consequently, the more pronounced the reduction in speed.
In addition to gravitational forces, air resistance and friction between the tires and the road also contribute to slowing down the car. Therefore, when the car encounters a hill, it experiences a reduction in speed due to the combined effects of gravitational forces, air resistance, and friction. The extent of this reduction depends on the specific characteristics of the hill, such as its slope and length, as well as factors related to the car itself, such as its mass and aerodynamics.