Question

A rubber cord catapult has cross-sectional area and initial length of rubber cord is It is stretched to 5 cm and then released to project a missile of mass Taking velocity of projected missile is

• A.
• B. $100 \mathrm {~ms} ^ { - 1 }$
• C. $250 \mathrm {~ms} ^ { - 1 }$
• D. $200 \mathrm {~ms} ^ { - 1 }$

Answer 1

Answer: (C)

$250 \mathrm {~ms} ^ { - 1 }$

Answer 2

Potential energy stored in the rubber cord catapult will be converted into kinetic energy of mass.

$\frac { 1 } { 2 } m v ^ { 2 } = \frac { 1 } { 2 } \frac { Y A l ^ { 2 } } { L }$⇒ $v = \sqrt { \frac { Y A l ^ { 2 } } { m L } }$

$= \sqrt { \frac { 5 \times 10 ^ { 8 } \times 25 \times 10 ^ { - 6 } \times \left( 5 \times 10 ^ { - 2 } \right) ^ { 2 } } { 5 \times 10 ^ { - 3 } \times 10 \times 10 ^ { - 2 } } } = 250 \mathrm {~m} / \mathrm { s }$