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NEET PHYSICSWORK, ENERGY AND POWERMedium

Question

A body of mass MM at rest explodes into three pieces, two of which of mass M/4M/4 each are thrown off in perpendicular directions with velocities of 3 m/s3 \text{ m/s} and 4 m/s4 \text{ m/s} respectively. The third piece will be thrown off with a velocity of:

A

1.5 m/s1.5 \text{ m/s}

B

2.0 m/s2.0 \text{ m/s}

C

2.5 m/s2.5 \text{ m/s}

D

3.0 m/s3.0 \text{ m/s}

Step-by-Step Solution

According to the law of conservation of linear momentum, since the body explodes due to internal forces, the total momentum of the system remains conserved . Initially, the body is at rest, so the initial momentum is zero.

Let the two pieces of mass M/4M/4 be moving along the x and y axes. Their momenta are: p1=M4×3i^=3M4i^\vec{p}_1 = \frac{M}{4} \times 3 \hat{i} = \frac{3M}{4} \hat{i} p2=M4×4j^=Mj^\vec{p}_2 = \frac{M}{4} \times 4 \hat{j} = M \hat{j}

The mass of the third piece is m3=MM4M4=M2m_3 = M - \frac{M}{4} - \frac{M}{4} = \frac{M}{2}. Let the velocity of the third piece be v3\vec{v}_3. Its momentum is p3=M2v3\vec{p}_3 = \frac{M}{2} \vec{v}_3.

By conservation of momentum: pinitial=pfinal\vec{p}_{\text{initial}} = \vec{p}_{\text{final}} 0=p1+p2+p30 = \vec{p}_1 + \vec{p}_2 + \vec{p}_3 0=3M4i^+Mj^+M2v30 = \frac{3M}{4}\hat{i} + M\hat{j} + \frac{M}{2}\vec{v}_3 M2v3=(3M4i^+Mj^)\frac{M}{2}\vec{v}_3 = -\left(\frac{3M}{4}\hat{i} + M\hat{j}\right) v3=1.5i^2j^\vec{v}_3 = -1.5\hat{i} - 2\hat{j}

The magnitude of the velocity is: v3=(1.5)2+(2)2=2.25+4=6.25=2.5 m/s|\vec{v}_3| = \sqrt{(-1.5)^2 + (-2)^2} = \sqrt{2.25 + 4} = \sqrt{6.25} = 2.5 \text{ m/s}.

Exam Context & Concepts Covered

This question aligns with the NEET PHYSICS syllabus, specifically targeting concepts from WORK, ENERGY AND POWER. Mastering this topic is crucial for scoring well in the upcoming medical entrance examinations. Solving conceptually related problems will help you understand the nuances of these concepts and improve your problem-solving speed.

PHYSICSWORK, ENERGY AND POWERexplodespiecesthrownperpendiculardirections

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