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# Free-body diagrams and Equilibrium Viva Questions and Answers

## Q: What is a free-body diagram?

A: A free-body diagram is a visual representation of the forces acting on an object, typically shown as arrows pointing in the direction of the force and labeled with the type of force and its magnitude.

## Q: Why are free-body diagrams important?

A: Free-body diagrams are important because they help us to understand the forces acting on an object and to apply the principles of mechanics to predict how the object will behave.

## Q: How do you draw a free-body diagram?

A: To draw a free-body diagram, first identify the object you want to analyze and then draw a dot to represent the object. Next, draw arrows to represent all the forces acting on the object, labeling each force with its type and magnitude.

## Q: What is equilibrium?

A: Equilibrium is a state in which the net force acting on an object is zero. In other words, the object is not accelerating and its velocity is constant.

## Q: What is static equilibrium?

A: Static equilibrium is a state in which an object is not moving and the net force acting on it is zero.

## Q: What is dynamic equilibrium?

A: Dynamic equilibrium is a state in which an object is moving at a constant velocity and the net force acting on it is zero.

## Q: How do you determine if an object is in equilibrium?

A: To determine if an object is in equilibrium, you must first draw a free-body diagram and then calculate the net force acting on the object. If the net force is zero, the object is in equilibrium.

## Q: What is the difference between balanced and unbalanced forces?

A: Balanced forces are forces that cancel each other out, resulting in a net force of zero. Unbalanced forces are forces that do not cancel each other out, resulting in a net force that causes acceleration.

## Q: How do you calculate the net force on an object?

A: To calculate the net force on an object, you must add up all the forces acting on the object, taking into account their direction and magnitude. If the net force is zero, the object is in equilibrium.

## Q: What is the difference between a vector and a scalar quantity?

A: A vector quantity has both magnitude and direction, while a scalar quantity has only magnitude. Examples of vector quantities include force and velocity, while examples of scalar quantities include mass and temperature.

## Q: How do you resolve a vector into its components?

A: To resolve a vector into its components, you must determine the vectorโs direction and then use trigonometry to calculate the magnitude of its x and y components.

## Q: What is the difference between a contact force and a non-contact force?

A: A contact force is a force that arises from physical contact between two objects, while a non-contact force is a force that acts at a distance without physical contact, such as gravitational or electromagnetic forces.

## Q: What is Newtonโs first law of motion?

A: Newtonโs first law of motion, also known as the law of inertia, states that an object will remain at rest or move at a constant velocity in a straight line unless acted upon by an external force.

## Q: What is Newtonโs second law of motion?

A: Newtonโs second law of motion states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass.

## Q: What is Newtonโs third law of motion?

A: Newtonโs third law of motion states that for every action, there is an equal and opposite reaction.

## Q: How do you calculate the weight of an object?

A: The weight of an object is equal to its mass multiplied by the acceleration due to gravity, which is approximately 9.8 m/s^2 near the Earthโs surface.

## Q: What is the difference between mass and weight?

A: Mass is a scalar quantity that measures the amount of matter in an object, while weight is a vector quantity that measures the gravitational force acting on an object.

## Q: How do you calculate the tension in a rope?

A: To calculate the tension in a rope, you must consider the forces acting on both ends of the rope and use Newtonโs second law of motion to solve for the tension force.

## Q: What is the difference between a force and a torque?

A: A force is a push or pull that acts on an object, while a torque is a twisting force that causes rotation around an axis.

## Q: What is the principle of moments?

A: The principle of moments states that for an object to be in equilibrium, the sum of the clockwise moments must be equal to the sum of the anticlockwise moments.

## Q: How do you calculate the moment of a force?

A: The moment of a force is equal to the magnitude of the force multiplied by the perpendicular distance from the line of action of the force to the axis of rotation.

## Q: What is the difference between a couple and a torque?

A: A couple is a pair of equal and opposite forces that act on an object at different points, causing a rotation around an axis. A torque, on the other hand, is a single force that causes a rotation around an axis.

## Q: What is the center of mass of an object?

A: The center of mass of an object is the point at which the objectโs mass can be considered to be concentrated, and the point around which the object will rotate if a torque is applied.

## Q: How do you calculate the center of mass of an object?

A: To calculate the center of mass of an object, you must determine the position and mass of each of its constituent parts, and then use a weighted average to determine the overall center of mass.

## Q: What is the difference between translational motion and rotational motion?

A: Translational motion is motion in which an object moves without rotating, while rotational motion is motion in which an object rotates around an axis without changing its position in space.

## Q: What is the moment of inertia of an object?

A: The moment of inertia of an object is a measure of its resistance to rotational motion, and depends on both the mass and the distribution of mass within the object.

## Q: How do you calculate the moment of inertia of an object?

A: The moment of inertia of an object depends on its shape and mass distribution, and can be calculated using a variety of mathematical formulas depending on the shape of the object.

## Q: What is angular momentum?

A: Angular momentum is a measure of an objectโs rotational motion, and is equal to the product of its moment of inertia and angular velocity.

## Q: What is conservation of angular momentum?

A: Conservation of angular momentum states that the total angular momentum of a system remains constant in the absence of external torques.

## Q: How do you calculate the torque required to accelerate an object?

A: To calculate the torque required to accelerate an object, you must use Newtonโs second law of motion and the objectโs moment of inertia to solve for the required torque.