Question

LSE

9. A car accelerates constantly from 3 m/s to 8 m/s in 10 s and then travel with
constant speed for another 7 s.
(a)
Sketch the speed-time graph.
(b)
Determine its acceleration for the first 10 s of the journey.
(c)
Calculate the total distance travelled by the car.​

Answer 1

b) initial speed (u)=3
final speed (v)=8
time (t)= 10
acceleration (a)=?

v=u+at
8=3+a(10)
5=10a
a=1/2= 0.5 m/s²

c)displacement (s)=?
1st section of journey

v ²=u ²+2as
8 ²=3 ²+2(0.5)s
64=9+1s
s=55meters

2nd section of journey
a=0
t=7
u=8
s=?

s=ut+1/2at²
s=8(7)+1/2(0)(7 ²)
s=56 meters

56+55= 111 meters

(For graph x axis =time (sec) & y axis= velocity (m/s))