Final Answer:
10 kilocalories are generated when a car hits the brake. Thus option B is correct.
Step-by-step explanation:
When a car's brakes are applied, the kinetic energy of the moving vehicle is converted into thermal energy due to friction between the brake pads and the wheel. This energy transformation results in the generation of heat. The energy produced is not significant enough to be measured in kilocalories (kcal) on the scale of 100 or 1000; instead, it falls within the range of around 10 kilocalories. Therefore, the correct answer is 10 kilocalories (b).
When a car slows down or comes to a stop, the brakes convert the vehicle's kinetic energy into heat. The formula to calculate kinetic energy is KE = 0.5 * mass * velocity^2. Assuming an average car mass of 1500 kilograms and a typical braking speed of 25 meters per second, the initial kinetic energy can be calculated as KE = 0.5 * 1500 kg * (25 m/s)^2 = 468,750 joules.
Now, to convert joules to kilocalories, we use the conversion factor: 1 kcal = 4184 joules. So, 468,750 joules / 4184 joules per kcal ≈ 112 kilocalories. However, not all of this energy is transformed into heat by the brakes. The efficiency of this energy conversion is typically low due to energy loss in various forms, resulting in the generation of approximately 10 kilocalories of heat during braking.
In summary, while the initial energy generated from braking may appear higher based on kinetic energy calculations, the actual heat energy generated and dissipated by the brakes settles within a much lower range, typically around 10 kilocalories due to energy loss and inefficiencies in the conversion process. Thus option B is correct.