Question

a car starting from rest moves with a constant acceleration of 5m/s² for 8 seconds. it then continues with a constant velocity, what distance will the car cover in 12s starting from rest?

Answer 1

For first 8 seconds:

Use second equation of motion:

s = ut + ½at²

t = 8 sec

u = 0

a = 5m/s²

thus

s = 0 + ½ 5 8²

s = 160 m.............................(1)

For the next (12-8=)4 seconds, velocity v is constant as no acceleration

v = u + at

v = 0 + 5 8

v = 40 m/s²

Now for constant velocity,

displacement = velocity x time

disp = 40 x 4 = 160 m...........................(2)

Add (1) and (2) for total displacement

160+160 = 320 m