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:

$a = \frac{\Delta v}{t}$

where:

• $a$ is acceleration,
• $\Delta v$ is the change in velocity,
• $t$ is the time taken.

Given:

• Initial velocity, $u = 2 \, \text{m/s}$
• Final velocity, $v = 20 \, \text{m/s}$
• Time, $t = 12 \, \text{s}$

Using the formula:

$a = \frac{v - u}{t}$

Substituting the values:

$a = \frac{20 - 2}{12} = \frac{18}{12} = 1.5 \, \text{m/s}^2$

To find the distance from the velocity-time graph:

The area under the graph gives the distance covered. The graph shows a triangle with a base of 15s and a height of 7m/s.

The area of the triangle is:

$\text{Area} = \frac{1}{2} \times \text{base} \times \text{height}$

$= \frac{1}{2} \times 15 \times 7 = 52.5 \text{ m}$

Thus, the distance the cyclist travels is 52.5 m.

Factors involving the driver include:

• Change in reaction time: A tired or distracted driver may take longer to react, increasing stopping distance.
• Effect of drugs: Substances can impair judgment and reaction times, thus increasing the stopping distance.
• Type of footwear: Footwear with poor grip can affect how quickly a driver can apply brakes effectively.

Factors involving the car and road include:

• Mass/weight of the car: Heavier cars require a longer distance to stop.
• Condition of brakes: Worn brakes will be less effective, increasing stopping distance.
• Type and state of tires: Worn or under-inflated tires have reduced grip, leading to increased stopping distances.
• State of the road: Wet or icy conditions can drastically increase stopping distance due to reduced friction.