Question

A swing hangs from a beam 10 feet high, with the seat hanging 2 feet above the ground. In motion, the swing moves back and forth from -130° to -50° to the horizontal. How far forward and back does the swing move along the ground at the extremes?

Answer 1

11.17 ft

Explanation:

Since the swing hangs from a beam 10 feet high with the seat hanging 2 feet above the ground, the swing moves in an arc of radius r = 10 ft - 2 ft = 8 ft.

Now, since the swing moves back and forth from -130° to -50° to the horizontal, the length of arc L it moves in is given by

L = Δθ/360 × 2πr where Δθ = change in angle of the swing = θ₂ - θ₁ where θ₁ = -50° and θ₂ = -130°. So, Δθ = θ₂ - θ₁ = -130° -(-50°) = -130° + 50° = -80°.

Substituting r and Δθ into L, we have

L = -80°/360° × 2π(8 ft)

= -8/36 × 16π ft

= -32π/9 ft

= -100.53/9 ft

= -11.17 ft

Ignoring the negative sign, the length of arc L = 11.17 ft. So, the swing moves back and forth 11.17 ft