Question

A 120 g mass has a velocity at a certain instant. Its kinetic energy is :

• A. 3 J
• B. 4 J
• C. 5 J
• D. 1.74 J

Answer 1

Answer: (D)

1.74 J

Answer 2

Here, $\mathrm { m } = 120 \mathrm {~g} \times 10 ^ { - 3 } \mathrm {~kg} = 0.12 \mathrm {~kg}$

Kinetic energy, $\mathrm { k } = \frac { 1 } { 2 } \mathrm {~m} \cdot \mathrm { v } ^ { 2 }$

$= \frac { 1 } { 2 } \times 0.12 \mathrm {~kg} \times \left( 29 \mathrm {~m} ^ { 2 } \mathrm {~s} ^ { - 2 } \right)$=1.74J