Given data

• Mass of child: $m = 5\,\text{kg}$
• Time period of rotation: $T = 3.14\,\text{s}$
• Radius: $r = 2\,\text{m}$

Formula for centrifugal force The magnitude of centrifugal force (same as centripetal force in magnitude, in the rotating frame) is $F = m\omega^2 r$ where angular speed $\omega = \frac{2\pi}{T}$

Calculate angular speed $\omega = \frac{2\pi}{3.14}$ Since $\pi \approx 3.14$, $\omega = \frac{2\times 3.14}{3.14} = 2\,\text{rad/s}$

Calculate force $F = m\omega^2 r = 5 \times (2)^2 \times 2$ $F = 5 \times 4 \times 2 = 40\,\text{N}$

Match with options

• A: $50\,\text{N}$
• B: $80\,\text{N}$
• C: $100\,\text{N}$
• D: $40\,\text{N}$

Therefore, the correct option is D.

Comparison with stored answer Stored correct answer: D

My derived answer also gives D.