Final answer:
These college-level physics questions involve calculating stopping distances for a car on different road surfaces. The problems require understanding friction, deceleration, and reaction time. The tasks include finding distances necessary to stop a car and analyzing skid marks to estimate speed.
Step-by-step explanation:
The subject matter of these questions involves the principles of physics, specifically the dynamics of how vehicles stop under different road conditions such as dry concrete, wet concrete, and ice. This application of physics is critical for understanding the forces at work and how they influence stopping distances during driving. The questions also incorporate the concept of a coefficient of friction (μ), which plays a vital role in defining how a car can decelerate and come to a halt. These questions are typically at a college level, where students are required to apply mathematical calculations to real-world scenarios in physics.
Calculating Stopping Distances
For example, the calculation of stopping distances on dry and wet concrete requires understanding and applying the formula for stopping distance, which relates the initial velocity, deceleration rate, and coefficient of friction between the car tires and the road surface:
μ = 0.55 for dry concrete
μ = 0.100 for ice
Using these coefficients, we perform calculations to determine how long it takes for a vehicle traveling at a certain speed to come to a complete stop under various conditions.
Examples of Calculations
Displacement Calculation: A car moving at 30.0 m/s decelerates at 7.00 m/s² on dry concrete versus 5.00 m/s² on wet concrete. Without reaction time, this gives us two different stopping distances for dry and wet conditions. With a reaction time of 0.500 s factored in, we must also calculate the additional distance traveled during this time before braking begins.
Speed Limit Enforcement: When a driver leaves a skid mark of 30.5 m after an emergency stop, a police officer can estimate the car's speed by analyzing these skid marks and may issue a speeding ticket based on presumed speed prior to deceleration.