Question

An object starting from rest covers 20metres in
first 2 seconds and 160 metres in next 4 seconds. What
Is its velocity after 7 seconds from the steart?​

Answer 1

as the object starts from rest, so initial velocity(u)=0

distance travelled(s) in first 2 seconds=20m

now as we know,

s=ut+1/2at²

20=0×2+1/2×a×(2)²

a=10 m/s²(acceleration)

now velocity(v) after 2 seconds can be found by using the formulae:-

v=u+at

 =0+10×2

 =20 m/s

now when 4 seconds has passed then the distance travelled(s) is 160 meters.

so the acceleration at 4 seconds is:-

now u=20 m/s

s=ut+1/2at²

160m=20m/s×4+1/2a(4)²

a=10 m/s²

so with uniform acceleration velocity at the end of 7 seconds is :-

v=u+at

v=0+10×7

v=70 m/s ANSWER