Question

Physics practice question

How long does it take an automobile traveling in the left lane of a highway at 55.0 km/h to overtake (become even with) another car that is traveling in the right lane at 25.0 km/h when the cars' front bumpers are initially 70 m apart?

________ s

Answer 1

1 km = 1000 m

1 hour = 3600 sec

Speed of the first automobile = V₁ = 55 km/hr = 55 x (1000/3600) m/s = 15.278 m/s

Speed of the second automobile = V₂ = 25 km/hr = 25 x (1000/3600) m/s = 6.944 m/s

Time taken by the first automobile to overtake the other automobile = T

Distance traveled by the first automobile in this time = D₁

D₁ = V₁T

Distance traveled by the second automobile in this time = D₂

D₂ = V₂T

Initial distance between the bumpers of the cars = D = 70 m

D = D₁ - D₂

D = V₁T - V₂T

D = (V₁ - V₂)T

70 = (15.278 - 6.944)T

T = 8.4 sec

Time taken by the automobile in the left lane to overtake the car in right lane = 8.4 sec