Question

V=20Km/h d=500m. t=? s V=20km/h=?m/s. d=500m/t=? S ​

Answer 1

$v = \frac{20km}{h} = \frac{20000m}{3600s} = \frac{200m}{36s} = \frac{50m}{9s}$

$\frac{50m}{9s} = \frac{500m}{t}$

$t = \frac{500 \times 9}{50} = 10 \times 9 = 90s$

Answer 2

$\vec{v}=20 \ km/h \\ d=500 \ m=0,5 \ km \\ \vec{v}=\frac{d}{t} \ \Rightarrow t=\frac{d}{\vec{v}}=\frac{0,5 \ km}{20 \ km/h}=0,025 \ h \\ \Rightarrow \boxed{t=90 \ s}$