A car of mass 1100 kg moves at 18 m/s. The brakes give a steady force of 4950 N against the motion…

Step 1. (a) Kinetic energy. $\tfrac{1}{2} \times 1100\ \text{kg} \times (18\ \text{m/s})^2 = 178\,200\ \text{J}$.

Step 2. (a) Distance. $d = \dfrac{178\,200\ \text{J}}{4950\ \text{N}} = 36\ \text{m}$.

Step 3. (b) Twice the speed, four times the energy: $4 \times 36\ \text{m} = 144\ \text{m}$.