9 (a) Which of these is a vector? A energy B force C mass D work (b) (i) State the equation that relates acceleration to change in velocity and time taken - Edexcel - GCSE Physics - Question 9 - 2020 - Paper 1

The equation is given by: $a = \frac{\Delta v}{t}$
where $a$ is acceleration, $\Delta v$ is the change in velocity, and $t$ is the time taken.

To calculate the acceleration, we first determine the change in velocity:
$\Delta v = v_f - v_i = 20 m/s - 2 m/s = 18 m/s$
Now, we use the acceleration formula:
$a = \frac{\Delta v}{t} = \frac{18 m/s}{12 s} = 1.5 m/s^2$
Thus, the acceleration of the van is $1.5 m/s^2$.

The distance traveled can be found using the area under the velocity-time graph. Since the graph is a triangle, the area can be calculated as follows:

The formula for the area of a triangle is:
$\text{Area} = \frac{1}{2} \times \text{base} \times \text{height}$
Here, the base (time) is 15 s and the height (velocity) is 7 m/s (the maximum velocity at 15 s).
Thus,
$\text{Distance} = \frac{1}{2} \times 15 s \times 7 m/s = 52.5 m$
Therefore, the cyclist travels a distance of $52.5 m$.

The stopping distance of a car can be increased by several driver-related factors:

• Change in reaction time: A tired or distracted driver may react more slowly, increasing stopping distance.
• Tiredness: A fatigued driver may take longer to respond to hazards.
• Effect of drugs: Impairment from substances can severely reduce driver reaction time.
• Type of footwear: Wearing inappropriate footwear (like flip-flops) can hinder proper braking.
• Pedal pressure: How hard the driver presses the brake pedal can also influence stopping ability.

Several car and road factors that impact stopping distance include:

• Weight of the car: Heavier vehicles require more distance to stop due to increased momentum.
• Speed of the car: Higher speeds result in longer stopping distances due to the greater kinetic energy that must be dissipated.
• State of brakes: Worn brakes can lead to longer distances as they may not effectively slow down the vehicle.
• State of tyres: Poorly maintained tyres can reduce grip and increase stopping distances.
• State of road: Slippery or uneven road surfaces can significantly lengthen the distance a car needs to stop.