Question

A small stone falling vertically covers a distance y in the first two seconds, which is also
covered in the next second. The distance y is equal to
(1) 15 m
(2) 30 m
(3) 25 m
(4) 18 m​

Answer 1

Explanation:

After time t, distance covered by first stone is s=

2

1

gt

2

After time (t-1), distance travelled by second stone is s=u(t−1)+

2

1

g(t−1)

2

=20t−20+

2

1

g(t−1)

2

These distance must be equal at the time of overtaking,

Thus,

2

1

gt

2

=20t−20+

2

1

g(t−1)

2

or, 0=20t−20+

2

1

g(1−2t)

which gives, 20t−20+5−10t=0 (putting g=10)

or t=1.5

Put this t in equation for distance to get s=

2

1

gt

2

=

2

1

10(1.5)

2

=11.25m