Question

4. An object is dropped from a height of 20m. Calculate the a) speed of the object when it hits the ground. b) time it takes to fall through this height. (g=10m/s2 )​

Answer 1

Given :-

An object is dropped from a height of 20m.

To Find :-

Calculate the a) speed of the object when it hits the ground. b) time it takes to fall through this height.

Solution :-

We know that

v² - u² = 2as

u = 0 m/s [Because at first the object is at rest]

⇒ v² - u² = 2gh

⇒ v² - (0)² = 2(20)(10)

⇒ v² - 0 = 400

⇒ v² = 400

⇒ v = √(400)

⇒ v = 20 m/s

Now

v = u + gt

⇒ 20 = 0 + 10(t)

⇒ 20 = 10t

⇒ 20/10 = t

⇒ 2 = t

Therefore

Speed of object when it hits the ground is 20 m/s & Time taken to fall is 2 sec