Question

stone is dropped from a tower of height 490 m. If the acceleration due to gravity of the earth is 9.8 metre per second square, the time taken by the stone to reach the ground will be

2 points​

Answer 1

Given:-

→A stone is dropped from a tower

→Height of the tower=490m

→Acceleration due to gravity on earth=9.8m/s²

To find:-

→Time taken by the stone to reach the ground

Solution:-

In this case:-

•Acceleration due to gravity will be +9.8m/s² as the stone is freely-falling.

•Initial velocity of the stone will be zero as the stone was intially at rest.

By using the 2nd equation of motion,we get:-

=>h = ut+1/2gt²

=>490 = 0(t) + 1/2×9.8×t²

=>490 = 4.9t²

=>t² = 490/4.9

=>t² = 100

=>t = √100

=>t = 10s

Thus,time taken by the stone to reach the ground is 10 seconds.

Some Extra Information:-

The 3 equations of motion for a freely-falling body are:-

•v = u+gt

•h = ut+1/2gt²

•v²-u² = 2gh