Question

A car starts from rest and attains a velocity of 40 metres per second in 20 seconds. it maintains this velocity for 30 seconds and then comes to rest in 25 seconds.
1. sketch the velocity time graph for the motion.
2. Calculate the acceleration of the body.
3. Calculate the total distance covered by the body

Answer 1

acceleration= changevelocity/time

Answer 2

first 20 s
slope of v = a = 2 m/s^2
v = 0 + 2 t
x = (1/2)(2) t^2

at t = 20
v = 40 m/s
x = 400 m

from t = 20 to t = 50
v = 40 m/s
a = 0

at t = 50
v = 40
new a = -40/25
x = 400 + 40(30) = 1600

from t = 50 to t = 75
v = 40 - 40/25(t-50)
a = -40/25
x = 1600 +40(t-50) - 20/25(t-50)^2
x = 1600 + 20*25 = 2100 at end

Answer 3

AE=40
EO=20=2ms-2