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 after 7 s from the start.​

Answer 1

Answer:

From s=ut+

2

1

at

2

In first 2 s,

s=20m

20=

2

1

a(2)

2

=2a

a=10 m/s

2

Velocity at the end of 2 s is

v=u+at=0+10×2=20m/s

In next 4s, s=ut+

2

1

a

′

t

2

160=20×4+

2

1

a

′

(4)

2

80=8a

′

a

′

=10 m/s

2

It shows that acceleration is uniform. From v=u+at

v=0+10×7=70 m/s

Answer: (D) 70