## College Physics (4th Edition)

The tenth car pulls the eleventh car with a force of $100,000~N$
We can find the acceleration of the train: $v_f=v_0+at$ $a = \frac{v_f-v_0}{t}$ $a = \frac{4.0~m/s-0}{20.0~s}$ $a = 0.20~m/s^2$ We can consider the system of ten cars from car 11 to car 20. The force that car 10 exerts on car 11 accelerates this system. We can find the force $F$ that car 10 exerts on car 11: $F = ma$ $F = (10\times 5.0\times 10^4~kg)(0.20~m/s^2)$ $F = 100,000~N$ The tenth car pulls the eleventh car with a force of $100,000~N$