Question

An object starting from rest travels 20 m in first 2 s and 160 m in next 4 s. What will be the velocity of the after 7 s from the start.​

Answer 1

Given:

Initial velocity = u =0m/s

Distance traveled =S=20m

time =t=2sec.

From second equation of motion:

S=ut + 1/2 at²

20= 0*2+ 1/2a2²

20=2a

a=10m/s²

velocity at the end of 2sec:

V=u+at

=0+10*2

V=20m/s

After 4sec, it covers a distance of 160m

so,

160=20*4+1/2(a¹)4²

160=80+2a

8a¹=80

a¹=10m/s²

It shows acceleration is uniform.

So, velocity at end of 7 sec from start:

V=u+at

= 0 + 10*7

=70m/s

the velocity after 7 sec from the start is 70m/s