Define force in physics.
Define work done in physics.
A force $F$ acts on a mass $m$ along a straight line through a distance $s$. The mass has acceleration $a$, and its speed changes from an initial speed $u$ to a final speed $v$. State the work $W$ done by $F$.
Use your answer in (i) together with an equation of motion to show that the kinetic energy of a mass can be written as $\tfrac{1}{2} \times \text{mass} \times (\text{speed})^2$.
A resultant force of $3800\,\text{N}$ makes a car of mass $1500\,\text{kg}$ speed up from an initial speed of $15\,\text{m s}^{-1}$ to a final speed of $30\,\text{m s}^{-1}$. Calculate the distance moved by the car during this acceleration.
The same force is used to change the speed of the car from $30\,\text{m s}^{-1}$ to $45\,\text{m s}^{-1}$. Explain why the distance moved is different from that found in (i).