Question

A stone is dropped from the top of a tower .. when it has fallen by 5 meters another stone is a dropped from 25 meters below the top .. if both stones reach the ground at the same moment then height of the tower from the ground is??

a)45 meters
b)50 meters
c)60 meters
d)65 meters​

Answer 1

Answer:

45m

Explanation:

Velocity of particle (1) at 5m below top u1 = √2gh = √(2×10×5) =10 m/s

For particle (1), using 2nd equation of motion

20+h = 10t + ½ gt2 …..(i)

For particle (2), using 2nd equation of motion

h = ½ gt2 …..(ii)

Put equation (ii) in equation (i)

20 + ½ gt2 = 10t + ½ gt2

t = 2 sec.

Put in equation (ii)

h = ½ gt2

= ½ ×10 × 22

h = 20m

The height of the building = 25 + 20 = 45m

Answer 2

Answer:

1st option is the correct answer (a)

45 meters