The table shows the stopping distances for a car - OCR Gateway - GCSE Physics - Question 25 - 2021 - Paper 4

To analyze the graph:

From the graph, when the car begins to brake (at approximately 0.75 seconds), it stops completely by 2.25 seconds. The speed starts at 8 m/s and decreases to 0 m/s.

The area under the graph represents the distance traveled while braking. The graph forms a right triangle with:

1. Base (Time) = 2.25 s - 0.75 s = 1.5 s
2. Height (Velocity) = 8 m/s.

The area (distance traveled) can be calculated using:

ext{Area} = rac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 1.5 \times 8 = 6 \text{ m}.

Thus, the braking distance is confirmed to be 6 m.

Using the kinetic energy formula:

$KE = 0.5 \times m \times v^2$

Where:

• KE = 30,000 J
• m = 1,000 kg
• v is the velocity we need to find.

Rearranging the formula:

$v^2 = \frac{2 \times KE}{m} = \frac{2 \times 30,000}{1,000} = 60.$

Taking the square root: $v = \sqrt{60} \approx 7.75 \text{ m/s}.$

Thus, the velocity of the car is approximately 7.75 m/s.

Increased air flow is crucial for lorries because:

1. Heat Dissipation: Lorries typically carry heavier loads than cars, which means their brakes generate more heat due to the increased braking force needed to stop. Adequate air flow helps in dissipating this heat effectively, preventing brake fade.

2. Longer Distances: Lorries often operate over longer distances and may have to brake frequently, leading to greater heat accumulation. Enhanced air flow is essential to maintain brake performance over extended usage.

3. Safety: Given that lorries are larger and heavier, they pose a greater risk in case of brake failure. Ensuring effective cooling through improved air flow is therefore critical for safety.