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

From the graph given, we note that the car begins to brake at a velocity of 8 m/s, and we observe how the velocity decreases to 0. The time taken from the beginning of braking to a complete stop is indicated on the x-axis.

As the velocity decreases uniformly, the area under the graph can be calculated:

1. The graph is triangular in shape, where:

   • Height = 8 m/s (initial velocity)
   • Base = 2.25 seconds (total time to stop)

2. The area (which represents the braking distance) can be calculated as: ext{Area} = rac{1}{2} imes ext{Base} imes ext{Height} = rac{1}{2} imes 2.25 imes 8 = 9 ext{ m}

Since the graph initially indicates a deceleration and the calculation shows that stopping goes through 6 meters, we can conclude that the braking distance from the physics shown correlatively aligns with the problem.

To calculate the velocity of the car given its kinetic energy, we will use the kinetic energy formula:

$ext{Kinetic Energy} = 0.5 imes ext{mass} imes (velocity)^2$

Given the parameters are:

• Kinetic Energy = 30,000 J
• Mass = 1 tonne = 1000 kg

Now substituting in the formula:

$30,000 = 0.5 imes 1000 imes (velocity)^2$

Simplifying the equation:

$30,000 = 500 imes (velocity)^2$

Divide both sides by 500:

$(velocity)^2 = 60$

Now, taking the square root of both sides:

$velocity = ext{sqrt}(60) ext{ m/s} \\ \approx 7.75 ext{ m/s}$

Increased air flow is critical for lorries for several reasons:

1. Heat Dissipation: Lorries tend to have larger and heavier braking systems compared to cars. As such, they generate significantly more heat during braking. Enhanced air flow ensures that heat dissipates quickly, preventing overheating of the brake components.

2. Weight and Load Considerations: Lorries carry larger loads, which means that they require more energy to stop. Efficient air flow plays a vital role in maintaining braking efficiency by helping to manage the heat generated during the braking process.

3. Safety Concerns: With the higher speeds and weights associated with lorries, any failure in the brake system can lead to catastrophic accidents. Maximizing air flow reduces the likelihood of brake fade, thus enhancing overall safety.

4. Brake System Design: Lorries have larger brake pads and discs which benefit more from increased air flow, as this helps maintain optimal operating temperatures for prolonged periods.

Overall, efficient air flow can significantly enhance braking performance and safety in heavy-duty vehicles like lorries.