Question

5. An objects starting from rest travels 30 m distance in first 2 sec and next 240 m in next
4 sec. What will be velocity after 7 sec from the start?​

Answer 1

Answer:

At first -

u = 0 | v = ? |S = 20 | t = 2s | a = ?

S = ut + 1/2 at^2

=> 20 = 0 + 1/2 (a)(2)^2

=> (a)(2) = 20

Therefore at this instance a = 10m/s^2

And so v = u+at

v = 0 + (10)(2) = 20m/s

Secondly -

u = 20m/s |S = 160m | a = ? | v = ? | t = 4s

S = ut +1/2 at^2

=> 160 = 80 + 1/2 (a)(4)^2

=> 160 -80 = (8) (a)

=> 80 = (8)(a)

=> a = 10m/s^2

So now v = u +at

=> v = 20+ 40

=> v = 60m/s

Finally -

u = 0 | t = 7s | a= 10m/s | v = ? | S = ?

v = u+at

=> v = 0 + (7)(10)

=> v = 70m/s

Concluding it all , Velocity after 7 seconds from start was 70m/s .

Simple Equations as I would say there are some on Quora that make me scratch my head around the same number of times as the velocity here.

Yeah 70 , that's right.

Correct me if I am wrong, I am open to suggestions and alternate answers.