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Lesson: Solving Equilibrium-of-a-Rigid-Body Problems Using Lami's Rule

Sample Question Videos

Worksheet • 25 Questions • 2 Videos

Q1:

A home-built swing is suspended by a rope passing through two pulleys, 𝐡 and 𝐢 , whose ends meet at point 𝐴 where the swing is attached. The rope segments 𝐴 𝐡 and 𝐴 𝐢 make angles of 4 0 ∘ and 4 5 ∘ with the horizontal, respectively. When a child sits still on the seat, the tension in 𝐴 𝐡 is 199 N. Given that, in this condition, the system is in equilibrium, find the combined weight of the child and the seat π‘Š and the tension 𝑇 in the rope 𝐴 𝐢 , giving your answers to the nearest two decimal places.

  • A π‘Š = 2 8 0 . 3 6 N , 𝑇 = 2 1 5 . 5 9 N
  • B π‘Š = 2 8 0 . 3 6 N , 𝑇 = 1 5 3 . 0 3 N
  • C π‘Š = 1 4 1 . 2 5 N , 𝑇 = 1 5 3 . 0 3 N
  • D π‘Š = 1 4 1 . 2 5 N , 𝑇 = 2 1 5 . 5 9 N

Q2:

A particle is in equilibrium under the action of three coplanar forces of magnitudes 𝐹 N, 15 N, and 25 N. Given that the last two forces are perpendicular to each other, determine the value of 𝐹 .

  • A 5 √ 3 4 N
  • B 20 N
  • C 17.49 N
  • D 5 √ 1 7 N

Q3:

The diagram shows a body weighing 6.1 N suspended in equilibrium by two light, inextensible strings, 𝐡 𝐢 and 𝐴 𝐢 . Given that 𝐡 𝐢 = 2 . 4 c m , 𝐴 𝐢 = 3 . 2 c m , and the strings are perpendicular, find the tensions 𝑇 1 and 𝑇 2 .

  • A 𝑇 = 4 . 8 8 1 N , 𝑇 = 3 . 6 6 2 N
  • B 𝑇 = 1 0 . 1 7 1 N , 𝑇 = 8 . 1 3 2 N
  • C 𝑇 = 1 0 . 1 7 1 N , 𝑇 = 3 . 6 6 2 N
  • D 𝑇 = 4 . 8 8 1 N , 𝑇 = 8 . 1 3 2 N
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