A stone is dropped from 78.5 m ,after 1 sec,another stone is dropped,both reach the ground at the same time, calculate the speed of second ball.

To calculate the speed of the second stone, we can use the equation for free fall motion:

v = u + gt

where:
v is the final velocity (speed) of the stone,
u is the initial velocity (which is 0 since the stone is dropped),
g is the acceleration due to gravity (approximately 9.8 m/s² on Earth),
t is the time taken for the stone to reach the ground.

We can find the value of t by using the time given in the problem, which is 1 second. Both stones reach the ground at the same time, so the time taken by the first stone to reach the ground is also 1 second.

Now, let's calculate the speed of the second stone:

v = 0 + (9.8 m/s²) * 1 s
v = 9.8 m/s

Therefore, the speed of the second stone is 9.8 m/s.