The driver of a car travelling at 72 kmph observes the light 300 m ahead of him turning red. The traffic light is timed to remain red for 20 s before it turns green . If the motorist wisher to pass the light without stopping to wait for it t turn green , determine .
The required uniform acceleration of the car

Explanation

Given u = 72 kmph `= 72 xx (5)/(18) ms^(-1)`
`= 20 ms^(-1) , s = 300 m, t = 20s, a = ?, v = ?`
`s = ut +(1)/(2) at^(2)`
`300 = (20 xx 20) +(1)/(2) a (20)^(2)`
300 = 400+ 200a
200 a = - 100
`a = (-100)/(200) `
`a = - 0 . 5 ms^(-2)`