5. (a) What do you understand by the following terms as applied in physics?
(i) Couple of force
(ii) Centre of gravity
(iii) Centre of mass
Answer (1)
A couple of force consists of two equal and opposite forces acting on a body, creating a torque.
The centre of gravity is the point where the entire weight of the body appears to act.
The centre of mass is the point where the entire mass of the body is assumed to be concentrated.
These concepts are vital in physics for understanding equilibrium, motion, and stability of objects.
Explanation
Understanding the Problem We need to define the following terms as applied in physics: (i) Couple of force (ii) Centre of gravity (iii) Centre of mass
Defining Couple of Force (i) Couple of force: A couple of force is a pair of forces, equal in magnitude but opposite in direction, acting on a body at different points. These forces do not act along the same line. The net force due to a couple is zero, but it produces a torque or turning effect on the body. This torque is what causes the body to rotate.
Defining Centre of Gravity (ii) Centre of gravity: The centre of gravity of a body is the point where the entire weight of the body appears to act. It is the point at which the gravitational force can be considered to act when determining the torque due to the body's weight. For a uniform gravitational field, the centre of gravity coincides with the centre of mass.
Defining Centre of Mass (iii) Centre of mass: The centre of mass of a body is the point where the entire mass of the body is assumed to be concentrated. It is a weighted average of the positions of all the parts of the body, weighted by their masses. The centre of mass is important in dynamics because the motion of the centre of mass of a system is the same as if all the mass of the system were concentrated at that point and all external forces were applied to it.
Final Answer In summary:
A couple of force is a pair of equal and opposite forces that create a torque.
The centre of gravity is the point where the weight of the body appears to act.
The centre of mass is the point where the mass of the body is assumed to be concentrated.
Examples
Understanding these concepts is crucial in various real-life scenarios. For example, when designing a seesaw, knowing the center of mass helps in balancing it. Similarly, understanding couples helps in designing steering wheels in cars, where applying equal and opposite forces creates a turning effect. In construction, knowing the center of gravity is essential for ensuring the stability of structures.
