SS2: PHYSICS  1ST TERM

Scalars & Vectors  Week 15 Topics1 Quiz

Equations of Motion  Week 23 Topics1 Quiz

Projectile  Week 35 Topics

Equilibrium of Forces I  Week 44 Topics

Equilibrium of Forces II  Week 54 Topics

Stability of a Body  Week 64 Topics1 Quiz

Simple Harmonic Motion (SHM)  Week 74 Topics

Speed, Velocity & Acceleration & Energy of Simple Harmonic Motion  Week 85 Topics1 Quiz

Linear Momentum  Week 96 Topics1 Quiz

Mechanical Energy & Machines  Week 102 Topics1 Quiz
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Couple
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).
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.
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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