physics questions please help?

Question

1)A bus slows down uniformly from 72.1 km/h to 0 km/h in22.6 seconds.How far does it travel before stopping ?answere in units of m.
range betwee{168.333-275.283}

2)A car accelerates from rest at -3.05 m/s squared.
a)What is the velocity at the end of 6.4 seconds?answere in unit m
Range {-31.52 to -8.241}
b)What is the displacement after 6.4 seconds?answere in units of m
Range {-126.08 to -16.64}

3)A car traveling at 7.1 m/s acclerates 2.2 m/s squared to reach a speed of 11.0 m/s.
How long does it take for this acceleration to occur ?answere in units of s.
Range {0.568182 -5}



Thank you so much.I need the help and i need to get this homework done .

Answer 1

(1) v = 72.1km/h = 72100m/3600s = (721/36)m/s
a = - (721/36)/22.6 = -0.886(m/s^2)
S = 0.5*|a|*t^2 = 0.5*0.886*22.6^2 = 226(m)
(2a) v = at = (-3.05 m/s^2)*(6.4s) = -19.52(m/s) ≈ -20m/s
(2b) S = 0.5at^2 =0.5vt = 0.5*(-20)*6.4 = -64(m)
(3) t = (v2 - v1)/a = (11.0 - 7.1)/2.2 = 1.8 (s)
These are easy problems. Please improve your problem solving capability.