Question

A body of mass 8kg is moved by a force $x = 2 m$ and the final position is $x = 10$m. The initial speed is The final speed is

• A. 6 m/s
• B. 12 m/s
• C. 18 m/s
• D. 14 m/s

Answer 1

Answer: (A)

6 m/s

Answer 2

Increment in kinetic energy = work done

⇒ $\frac { 1 } { 2 } m \left( v ^ { 2 } - u ^ { 2 } \right) = \int _ { x _ { 1 } } ^ { x _ { 2 } } F . d x = \int _ { 2 } ^ { 10 } ( 3 x ) d x$

⇒ $\frac { 1 } { 2 } m v ^ { 2 } = \frac { 3 } { 2 } \left[ x ^ { 2 } \right] _ { 2 } ^ { 10 } = \frac { 3 } { 2 } [ 100 - 4 ]$

⇒ $\frac { 1 } { 2 } \times 8 \times v ^ { 2 } = \frac { 3 } { 2 } \times 96$ ⇒