Question

A car is travelling at 20 m per second along a road a children runs out into the road 50m ahead and the car driver steps on the brake pedal what was the car acceleration vs the car is stop just before it reaches the child

Answer 1

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һєяє' ʏȏȗя ѧṅśwєя ʟȏȏҡıṅɢ ғȏя________
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✯▶50 = Vi t + .5 a t^2 

♦v = Vi + a t = 0 at end 

so,
 
♦a = -Vi/t = -20/t 

50 = 20 t - .5 (20/t)t^2 

50 = 20 t - 10 t = 10 t 

▶t = 5 seconds 

a =-20/5 = -4 meters/second^2.

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Answer 2

✯▶50 = Vi t + .5 a t^2

♦v = Vi + a t = 0 at end

so,

♦a = -Vi/t = -20/t

50 = 20 t - .5 (20/t)t^2

50 = 20 t - 10 t = 10 t

▶t = 5 seconds

a =-20/5 = -4 meters/second^2