Class 9th Physics Chapter 4 Question Answer

Complete Notes of Class 9th Physics Chapter 4 Question Answer Turning Effect of Forces Numericals in 9th Class Physics Urdu Medium written by Sir Fahad Abbas Suib. These computerized notes are very helpful in the preparation of Turning Effect of Forces Numericals for students of the Class 9th Physics Chapter 4 Question Answer these are according to the paper patterns of all Punjab boards.

• Important Values and Important Formulas
• Turning Effect of Forces Exercise Numericals with Solutions in Urdu 
• LIKE AND UNLIKE PARALLEL FORCES: We often come across objects on which many forces are acting. In many cases, we find all or some of the forces acting on a body in the same direction. For example, many people push a bus to start it. Why all of them push it in the same direction? All these forces are applied in the same direction so these are all parallel to each other. Such forces which are parallel to each other are called parallel forces. 
• A bag with apples in it. The Weight of each apple weight of the bag is due to the weight of all the apples in it. Since the weight of every apple in the bag is the force of gravity acting on it vertically downwards, therefore, weights of apples are the parallel forces. All these forces are acting in the same direction. Such forces are called like parallel forces.
• "Like parallel forces are the forces that are parallel to each other and have the same direction".
• An apple is suspended by a string. Weight F1 The string is stretched due to weight of the apple. The forces acting on it are; weight of the apple acting vertically downwards and tension in the string pulling it vertically upwards. The two forces are parallel but opposite to each other. These forces are called unlike parallel forces. In forces F1 and F2 are also unlike parallel forces, because they are parallel and opposite to each other. But F1 and F2 are not acting along the same line and hence they are capable to rotate the body.
• "Unlike parallel forces are the forces that are parallel but have directions opposite to each other".
• Addition of forces class 9: Force is a vector quantity. It has both magnitude and direction; therefore, forces are not added by ordinary arithmetical rules. When forces are added, we get a resultant force. "A resultant force is a single force that has the same effect as the combined effect of all the forces to be added".
• Head to tail rule class 9: A graphical method of vector addition. First select a suitable scale. Then draw the vectors of all the forces according to the scale; such as vectors A and B. Take any one of the vectors as first vector e.g., vector A. Then draw next vector B such that its tail coincides with the head of the first vector A.
• Similarly draw the next vector for the third force (if any) with its tail coinciding with the head of the previous vector and so on. Now draw a vector R such that its tail is at the tail of vector A, the first vector, while its head is at the head of vector B, the last vector. Vector R represents the resultant force completely in magnitude and direction.
• Resolution of forces class 9: The process of splitting up vectors (forces) into their component forces is called resolution of forces. If a force is formed from two mutually perpendicular components then such components are called its perpendicular components. 
• "Splitting up of a force into two mutually perpendicular components is called the resolution of that force". 
• RIGID BODY: A body is composed of large number of small particles. If the distances between all pairs of particles of the body do not change by applying a force then it is called a rigid body. In other words, a rigid body is the one that is not deformed by force or forces acting on it.