Will a pedestrian have time to cross a 10 m wide road at a speed of 2 km / h if an approaching car

| July 25, 2021 | education

Will a pedestrian have time to cross a 10 m wide road at a speed of 2 km / h if an approaching car is traveling at a speed of 18 km / h. at the time of countdown, the car was at a distance of 600 m from the pedestrian crossing. how many seconds the pedestrian will or will not be in time.

L = 10 m.

Vp = 2 km / h = 0.55 m / s.

S = 600 m.

Vа = 18 km / h = 5 m / s.

t -?

Time t with uniform rectilinear motion is determined by the formula: t = S / V, where S is the path traveled by the body, V is the speed of the body.

Let us find the time tp of the pedestrian crossing the road according to the formula: tp = L / Vp.

tp = 10 m / 0.55 m / s = 18.2 s.

Let us find the time tа, during which the car will reach the pedestrian who is at the crossing, according to the formula: tа = S / Vа.

tа = 600 m / 5 m / s = 12 s.

The pedestrian will not have time to cross the road for the time t = tp – tа.

t = 18.2 s – 12 s = 6.2 s.

Answer: the pedestrian will not have time to cross the road for the time t = 6.2 s.



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