Question

A car moving along a straight highway with speed of 126 kmh–1 is brought to a stop within a distance of 200 m. What is the retardation of the car (assumed uniform) and how long does it take for the car to stop ?​

Answer 1

Given -

• Velocity (v) = 126 km/h
• Distance (s) = 200m

To Find

• Retardation (a)
• Time (t)

Formula

• s = u²/2a
• v = u + at

Solution

⟹ Convert km/h to m/s

v = 126 × 5/18

v = 35m/s

⟹ s = u²/2a

⟹ 200 = 35 × 35 /2a

⟹ 200 = 1225/2a

⟹ a = 1225/2×200

⟹ a = 1225/400

⟹ a = 3 m/s²

Time —

v = u + at

35 = 0 + 3×t

t = 35/3

t = 11.06s

Answer

Retardation = -3m/s²

time = 11.06s