Photo AI
The speed limit on many roads in towns is 13.5 m/s - AQA - GCSE Physics Combined Science - Question 6 - 2020 - Paper 2
Question 6
The speed limit on many roads in towns is 13.5 m/s. Outside schools this speed limit is often reduced by one-third. Calculate the reduced speed limit. Reduced speed... show full transcript
Worked Solution & Example Answer:The speed limit on many roads in towns is 13.5 m/s - AQA - GCSE Physics Combined Science - Question 6 - 2020 - Paper 2
Step 1
Step 2
Explain one other advantage of a reduced speed limit.
Answer
A reduced speed limit can lead to decreased stopping distances. This enhances road safety as vehicles traveling at lower speeds have a greater reaction time, reducing the severity of accidents. Additionally, lower speeds can minimize the risk of collisions, especially in areas with heavy pedestrian traffic.
Step 3
Calculate the minimum braking distance for the car at the speed it passed the speed camera.
Answer
To calculate the minimum braking distance, we first need to find the speed of the car:
Using the formula:
Distance = Speed × Time We know the car traveled 14 m in 0.70 s:
Speed, v = \frac{14 m}{0.70 s} = 20 m/s.
Now, using the kinematic equation:
( v^2 = u^2 + 2as ) where:
- v = final velocity = 0 (since the car stops)
- u = initial velocity = 20 m/s
- a = deceleration = -6.25 m/s² (negative as it is deceleration)
- s = stopping distance
egin{align*}
0 = (20)^2 + 2(-6.25)s
s = \frac{(20)^2}{2(6.25)} = \frac{400}{12.5} = 32 m
\end{align*}
Thus, the minimum braking distance is 32 m.
Step 4
Explain why the empty van has a shorter stopping distance than the full van.
Answer
The empty van experiences the same maximum force applied by the brakes as the full van. However, because the mass is less, there is a greater deceleration when the empty van brakes. Consequently, the braking distance is reduced. This means that with less mass, the kinetic energy of the van is lower at a given speed, leading to a shorter distance needed to bring the van to a stop.