Question

an object starts from rest and travel 20 metre first second and 160m in next sec find its velocity 7sec after the start ​

Answer 1

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

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