Maharashtra State BoardSSC (Marathi Semi-English) 9th
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# Solve the Following Example. a Bullet Having a Mass of 10 G and Moving with a Speed of 1.5 M/S, Penetrates a Thick Wooden Plank of Mass 90 G. the Plank Was Initially at Rest. the Bullet Gets - Science and Technology

#### Question

Solve the following example.
A bullet having a mass of 10 g and moving with a speed of 1.5 m/s, penetrates a thick wooden plank of mass 90 g. The plank was initially at rest. The bullet gets embedded in the plank and both move together.  Determine their velocity.     (Ans: 0.15 m/s)

#### Solution

Mass of bullet, m= 10 g
Initial speed of bullet, u= 1.5 m/s
Mass of plank, m= 90 g
Initial speed of plank, u= 0
From law of conservation of momentum,
m1u1 + m2u2 = m1v+ m2v2
Since, the bullet gets embedded in the palnk and both move with the same speed, so v= v= v
So, we can rewrite the equation as
m1u1 + m2u2 = (m1 + m2)v
10 xx 1.5 + 90 xx 0 = (10 + 90)v
15 = 100 v
⇒ v = 0.15 m/s

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