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SS2: PHYSICS - 1ST TERM

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  1. Scalars & Vectors | Week 1
    5 Topics
    |
    1 Quiz
  2. Equations of Motion | Week 2
    3 Topics
    |
    1 Quiz
  3. Projectile | Week 3
    5 Topics
  4. Equilibrium of Forces I | Week 4
    4 Topics
  5. Equilibrium of Forces II | Week 5
    4 Topics
  6. Stability of a Body | Week 6
    4 Topics
    |
    1 Quiz
  7. Simple Harmonic Motion (SHM) | Week 7
    4 Topics
  8. Speed, Velocity & Acceleration & Energy of Simple Harmonic Motion | Week 8
    5 Topics
    |
    1 Quiz
  9. Linear Momentum | Week 9
    6 Topics
    |
    1 Quiz
  10. Mechanical Energy & Machines | Week 10
    2 Topics
    |
    1 Quiz



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A couple is a system of two equal and parallel but opposite forces not acting in a straight line. This system of forces in parallel can cause a body to rotate and not move in a straight line (linearly).

couple
Fig. 1 – Wheel of a bicycle.

The moment of a couple is the product of one of the forces and the perpendicular distance between the lines of action of the two forces.

From figure 1 above;

Moment of a couple = Force x perpendicular distance

Moment = F x d

Moment = F x 2r

where r is the radius of the wheel and d is its diameter.

Screenshot 2022 07 06 at 02.07.41
Fig. 2

In figure 2 above;

Moment of a couple = \(\scriptsize F \: \times \: x \)

The perpendicular distance between the lines of action of two equal and opposite forces is known as the arm of the couple. In fig. 1 the arm of the couple is (d), while in fig. 2 the arm of the couple is (x).

The magnitude of the couple (i.e. moment of a couple) is the product of one of the forces and the arm of the couple.

The moment of a couple is also called a torque.

Applications of Torque:

Some of the applications of torque or moment of couple include;

1. The easiness to turn a tap on or off by applying two equal and parallel forces compared to applying a single force.
2. It is easier to turn a steering wheel of a vehicle by applying a couple using two hands instead of a single force with one arm.
3. The wind vane.
4. Spinning top.

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