Question

The driver of a car travelling at 52 km/h
applies brakes and decelerates uniformly. The car stops
in 5 s. Another driver going at 34 km/h applies brakes
slowly and stops in 10 s. On the same graph paper, plot
the speed versus time graph for the two cars. Which
of the two cars travelled farther after the brakes were
applied?
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Answer 1

Distance Travelled by first car before coming to rest =Area of Δ OPR

= (1/2) x OR x OP

= (1/2) x 5 s x 52 kmh-1

= (1/2) x 5 x (52 x 1000) / 3600) m

= (1/2) x 5x (130 / 9) m

= 325 / 9 m

= 36.11 m

Distance Travelled by second car before coming to rest =Area of Δ OSQ

= (1/2) x OQ x OS

= (1/2) x 10 s x 3 kmh-1

= (1/2) x 10 x (3 x 1000) / 3600) m

= (1/2) x 10 x (5/6) m

= 5 x (5/6) m

= 25/6 m

= 4.16 m