Question

a body of mass 5kg is dropped frm a height of 20m. calculate the initial momentum and the momentum just before it strikes the ground

Answer 1

Given :-

• Mass of body, m = 5 kg
• Height of the body, s = 20 m
• g = 10 m/s
• u = 0 m/s

To Find :-

Initial momentum and the moment just before it strikes the ground.

Solution :-

First, we can find the initial momentum:

Initial momentum = mu

⇒ 4×0

⇒ 0 kg m/s

Then, we using the third equation of motion,

⇒ v^2 - u^2 = 2as

⇒ v^2 - 0^2 = 2×10×20

⇒ v^2 = 400

⇒ v = √400

⇒ v = 20 m/s

Final momentum :- mv

⇒ 4 × 20

⇒ 80 kg m/s

Hence initial momentum= 0 kg m/s and final momentum = 80 kg m/s.

Answer 2

$\green{\large\underline{\underline\mathtt{Given}}}$

• Mass of body = 5kg
• Height of body = 20m

$\orange{\large\underline{\underline\mathtt{To\:Find}}}$

• Initial momentum
• Final momentum

$\blue{\large\underline{\underline\mathtt{Solution}}}$

We can find the initial momentum :-

Also given that,

• g = 10 m/s
• u = 0 m/s

We know that,

★ Initial Momentum = m × u

Put the values,

=> 5 × 0

=> 0 kg m/s.

Next, we can find the momentum just before it strikes the ground :-

We using the third equation of motion,

★ v² - u² = 2as

=> v² - 0² = 2×10×20

=> v² = 400

=> v = √400

=> v = 20 m/s.

We know that,

★ Final Momentum = m × v

=> 5 × 20

=> 100 kg m/s.

Hence,

• Initial momentum = 0 kg m/s.
• Final momentum = 100 kg m/s.