Final answer:
The student can calculate the time and distance needed for a car to stop using the mass of the car, the initial speed, and the coefficient of friction, applying equations of motion and Newton's laws.
Step-by-step explanation:
To determine the time and distance necessary for a 621 kg car initially moving at 16.8 m/s to stop, we'll use the coefficient of friction between the tires and the road (0.7) and the equation of motion. The force due to friction (F) can be calculated using F = μ * m * g, where μ is the coefficient of friction, m is the mass of the car, and g is the acceleration due to gravity (9.81 m/s²). Once we've found the force, we can find the acceleration (a) by using Newton's second law, F = m * a. To find the deceleration a = F / m.
The deceleration a = (0.7 * 621 kg * 9.81 m/s²) / 621 kg = 0.7 * 9.81 m/s². Now, we can find the time (t) taken to stop using the equation v = u + at, where v is the final velocity, u is the initial velocity, and a is the acceleration. After rearranging, t = (v - u) / a.
With the car stopping, v = 0, so t = (0 - 16.8 m/s) / (-0.7 * 9.81 m/s²). The negative signs indicate deceleration. Finally, we can calculate the stopping distance using the equation s = ut + (1/2)at².
By calculating these values, we can provide the time to stop and the distance covered, demonstrating important principles of physics and motion.