Answer to Question #168328 in Physics for Nasratullah Darwish

Question

A train travelling 72 km/h undergoes a uniform retardation (deceleration)of 2ms ^-2 when the breaks are applied. Find the time taken to come to rest and the distance travelled from the place where the breaks were applied

Answer 1

(a)

$$t=\dfrac{v-v_0}{a},$$ $$t=\dfrac{0-20\ \dfrac{m}{s}}{-2.0\ \dfrac{m}{s^2}}=10\ s.$$

(b)

$$d=\dfrac{1}{2}(v+v_0)t,$$ $$d=\dfrac{1}{2}\cdot(0+20\ \dfrac{m}{s})\cdot10\ s=100\ m.$$