In 1993, Ileana Salvador of Italy walked 3.0 km in under 12.0 min. Suppose that during 115 m of her walk Slavador is observed to steadily increase her speed from 4.20 m/s to 5.00 m/s. How long does this increase in speed take?

Solution:-

v_i =+245km/h
a_avg = -3.0m/s²

v_f =v_i -(0.200)v_i


v_i =(245km/h)(1h/3600s)(103m/1km)= +68.1m/s

v_f =(1.000-0.200)v_i =(0.800)(68.1m/s)=+54.5m/s

Δt=v_f -v_i /a_avg

  = 54.5m/s - 68.1m/s / -3.0m/s²


  =-13.6m/s /-3.0 m/s²

  =  4.5s