Physics - Stopping Distances

What is the formula for stopping distances?

\[\text{stopping distance} = \text{thinking distance} + \text{braking distance}\]

What affects reaction time in the context of stopping distances?

What are the two factors that affect stopping distance?

Assuming a constant velocity ($v$) during reaction time, what is the formula for thinking distance?

\[s = vt\]

What are the three factors that affect braking distance?

What things can affect the breaking force?

A larger vehicle mass has what affect on braking distance?

A larger breaking distance.

When a car is in motion, what’s the kinetic energy of the car?

\[\frac{1}{2} m v^2\]

Where is the kinetic energy of a car transferred to when braking?

Transferred to the thermal store of the breaks and the surroundings.

What is the work done by a car when it’s breaking?

\[W = F \times s\]

When a car is breaking and the energy is being calculated by $W = F \times s$, what does $F$ represent?

The breaking force of the car.

What are the units for work done?

joules, $J$

What must be true about the kinetic energy of a car and the work done when breaking?

They must be equal.

What is the formula for the kinetic energy of a car in relation to work done?

\[\frac{1}{2} m v^2 = F \times s\]

What is the formula for breaking distance involving mass, velocity and breaking force?

\[\frac{1}{2} m v^2 = F \times s\]

What is the formula for breaking distance involving velocity and acceleration?

\[\text{breaking distance} = \frac{(initial velocity)^2}{2 \times \text{acceleration}}\]

What does a $2\times$ initial velocity translate to in terms of breaking distance?

$4\times$ the breaking distance.

The breaking distance equation involving velocity and acceleration is a special case of which SUVAT equation?

\[v^2 = u^2 + 2as\]

If a truck is exerts a breaking force of $8700N$ and has a mass of $2300kg$, how could you calculate the acceleration?

\[\text{8700N}{2300kg} \\\\ F = ma\]