Question

A body of mass 2 kg is dropped from a height of 20 m. It accelerates uniformly at the rate of 10 m/s2until it hits the ground. Calculate the initial momentum and the momentum just before it strikes the ground.

Answer 1

Given :

➳ Mass of body = 2kg

➳ Initial velocity = zero (freefall)

➳ Acc. due to gravity = 10m/s²

To Find :

➔ Initial momentum.

➔ Final momentum just before it strikes the ground.

SoluTion :

⇒ Momentum is defined adms the product of mass and velocity.

⇒ It is a vector quantity having both magnitude as well as direction.

⇒ SI unit : kg m/s or N s

⇒ For a body falling freely under the action of gravity, g is taken positive.

✴ Final velocity at which body hits the ground :

➠ v² - u² = 2gH

➠ v² - (0)² = 2(10)(20)

➠ v² = 400

➠ v = √400

➠ v = 20 m/s

✴ Initial momentum :

➛ Pi = m × u

➛ Pi = 2 × 0

➛ Pi = 0 Ns

✴ Final momentum :

⟶ Pf = m × v

⟶ Pf = 2 × 20

⟶ Pf = 40 Ns