A car is travelling along a straight road at 20 m s−120\text{ m s}^{-1}20 m s−1. The driver sees an obstacle and after 0.45 s0.45\text{ s}0.45 s applies the brakes. The stopping distance of the car is 41 m41\text{ m}41 m.
Calculate the magnitude of the deceleration of the car when the brakes are applied.
A student slides a wooden block at different initial speeds along a horizontal table to model braking.
The student wishes to investigate how the sliding distance sss before the block comes to rest depends on its initial speed uuu.
The speed uuu and distance sss are related by the equation \
\frac{1}{2}mu^2 = fs{\char"24}$ where $m$ is the mass of the block and $f$ is the constant frictional force acting on the block. * Describe how an experiment can be conducted in the laboratory to investigate the relationship between $u$ and $s$. * Explain how the data can be analysed to determine $f$.
