Question

A stone is dropped from the top of a 80 m high tower. Calculate its speed after 2s. Also find the speed with which it strikes the ground.​

Answer 1

Given that,

Height = 40 m

Time t =2 sec

We know that,

v=u+gt

v=0+9.8×2

v=19.6m/s

The speed of stone is 19.6 m/s

Now, the speed with which the stone strikes the ground

v

2

=u

2

+2gs

v

2

=0+2×9.8×40

v

2

=784

v=28m/s

Hence, the speed with which the stone strikes the ground is 28 m/s

PLEASE MARK IT BRAINLIST

Answer 2

Answer:

The speed with which it strikes the ground is 20 (2^1/2) m/s.

Step-by-step explanation:

Given:

• A stone is dropped from the top of a 80m high tower.

To Find:

The speed after 2 sec.

Solution:

The speed with which it striked the ground = ?

Using the formula,

V = u + at

=> V = 0 + (9.8)(20)

=> V = 10.6 m/s.

Now,

To find the time, t = ?

S = ut + 1/2 at²

=> 40J = (0)t + 1/2 + (10)t²

=> t² = 40/5

=> t² = 8

=> t = 8^1/2.

Here,

V = u + at

=> 0 + (10^1/8)

=> 20 (2^1/2) m/s.

Therefore, The speed with which it strikes the ground id 20 (2^1/2) m/s.