Question

A car is moving 14.4 m/s when it hits the brakes. It slows for 78.8 m, which takes 9.92 s. IT then accelerates at 1.83 m/s2 for 4.50 s. What is its final velocity?

Answer 1

Answer:

12.415m/s

Explanation:

intial velocity of car is 14.4m/s when it brakes it slows which means it has retardation (negative acceleration) covering the distance of 78.8m in 9.92 seconds

now

using Newton's second equation of motion

s=ut+1/2at²

78.8=(14.4*9.92)+1/2a(9.92)²

a=-1.301m/s²

minus sign indicates retardation

now using Newton's first equation of motion

v=u+at

v=14.4+(-1.031)9.92

v=4.18m/s

now car from there when it's velocity becomes 4.18m/s² it accelerates again from its previous velocity

again using Newton's first equation of motion

v=u+at

v=4.18+(1.83*4.5)

v=12.415m/s