see the problem below this one.
for each stage, the distance s = v0*t + 1/2 at^2
A car starting from rest& moves for 20 seconds its velocity reach 5m/s & moves at this velocity for 30 seconds.it's velocity increases to 10m/s over 10 seconds.it moves at this velocity for 40 seconds &then slows down to come to rest after further 60 seconds.how far did the car travel during this time?and during which period was the accleration of the car the lowest and during which period period was the accleration of the car the highest?
3 answers
I don't understand
Phase 1
v = Vi + a t
5 = 0 + a * 20
a = 1/4
x = 0 + 0 t + (1/2) a t^2
x = (1/8)(400) = 50 meters
============================
Phase 2
Xi = 50
Vi = 5 for next 30 s
a = 0
v = Vi + a t = Vi = 5
x = Xi + Vi t + (1/2) a t^2
x = 50 + 5 t = 50 + 5(30) = 200
Phase 3
Xi = 200
Vi = 5
v after 10 s = 10 m/s
v = Vi + a t
10 = 5 + a * 10
5 = 10 a
a = 0.5 m/s^2
x = Xi + Vi t +(1/2)a t^2
x = 200 + 5(10) + (1/2)(0.5)(100)
x = 200 + 50 + 25 = 275
=========================
Phase 4
Xi = 275
Vi = 10 m/s
a = 0 for 40 seconds
x = Xi + 10*40 = 275 + 400 = 675 meters
===================================
Phase 5
Xi = 275
Vi = 10 m/s
stops in 60 seconds
v =10 + a (60)
0 = 10 + 60 a
a = - (1/6) meter/second^2
x = 675 + 10(60) -(1/2)(1/6)(3600)
x = 675 + 600 - 300 = 975 meters for the whole trip
v = Vi + a t
5 = 0 + a * 20
a = 1/4
x = 0 + 0 t + (1/2) a t^2
x = (1/8)(400) = 50 meters
============================
Phase 2
Xi = 50
Vi = 5 for next 30 s
a = 0
v = Vi + a t = Vi = 5
x = Xi + Vi t + (1/2) a t^2
x = 50 + 5 t = 50 + 5(30) = 200
Phase 3
Xi = 200
Vi = 5
v after 10 s = 10 m/s
v = Vi + a t
10 = 5 + a * 10
5 = 10 a
a = 0.5 m/s^2
x = Xi + Vi t +(1/2)a t^2
x = 200 + 5(10) + (1/2)(0.5)(100)
x = 200 + 50 + 25 = 275
=========================
Phase 4
Xi = 275
Vi = 10 m/s
a = 0 for 40 seconds
x = Xi + 10*40 = 275 + 400 = 675 meters
===================================
Phase 5
Xi = 275
Vi = 10 m/s
stops in 60 seconds
v =10 + a (60)
0 = 10 + 60 a
a = - (1/6) meter/second^2
x = 675 + 10(60) -(1/2)(1/6)(3600)
x = 675 + 600 - 300 = 975 meters for the whole trip