Question

an object starting from rest travels 20m in first 2 seconds 160 metre in next 4 seconds.find the velocity of the object after 7 seconds from the start?​

Answer 1

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

Explanation:

Given:

Initial velocity = u =0m/s

Distance travelled =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