Solution Manual for Fluid Mech Cengel Book
Chapter 6 Momentum Analysis of Flow Systems
Chapter 6 MOMENTUM ANALYSIS OF FLOW SYSTEMS
Newton’s Laws and Conservation of Momentum 6-1C Newton’s first law states that “a body at rest remains at rest, and a body in motion remains in motion at the same velocity in a straight path when the net force acting on it is zero.” Therefore, a body tends to preserve its state or inertia. Newton’s second law states that “the acceleration of a body is proportional to the net force acting on it and is inversely proportional to its mass.” Newton’s third law states “when a body exerts a force on a second body, the second body exerts an equal and opposite force on the first.” r 6-2C Since momentum ( mV ) is the product of a vector (velocity) and a scalar (mass), momentum must be a vector that points in the same direction as the velocity vector.
6-3C The conservation of momentum principle is expressed as “the momentum of a system remains constant when the net force acting on it is zero, and thus the momentum of such systems is conserved”. The momentum of a body remains constant if the net force acting on it is zero. 6-4C Newton’s second law of motion, also called the angular momentum equation, is expressed as “the rate of change of the angular momentum of a body is equal to the net torque acting it.” For a non-rigid body with zero net torque, the angular momentum remains constant, but the angular velocity changes in accordance with Iω = constant where I is the moment of inertia of the body. 6-5C No. Two rigid bodies having the same mass and angular speed will have different angular momentums unless they also have the same moment of inertia I. Linear Momentum Equation 6-6C The relationship between the time rates of change of an extensive property for a system and for a control volume is expressed by the Reynolds transport theorem, which provides the link between the r system and control volume concepts. The linear momentum equation is obtained by setting b = V and thus r B =
Chapter 6 MOMENTUM ANALYSIS OF FLOW SYSTEMS
Newton’s Laws and Conservation of Momentum 6-1C Newton’s first law states that “a body at rest remains at rest, and a body in motion remains in motion at the same velocity in a straight path when the net force acting on it is zero.” Therefore, a body tends to preserve its state or inertia. Newton’s second law states that “the acceleration of a body is proportional to the net force acting on it and is inversely proportional to its mass.” Newton’s third law states “when a body exerts a force on a second body, the second body exerts an equal and opposite force on the first.” r 6-2C Since momentum ( mV ) is the product of a vector (velocity) and a scalar (mass), momentum must be a vector that points in the same direction as the velocity vector.
6-3C The conservation of momentum principle is expressed as “the momentum of a system remains constant when the net force acting on it is zero, and thus the momentum of such systems is conserved”. The momentum of a body remains constant if the net force acting on it is zero. 6-4C Newton’s second law of motion, also called the angular momentum equation, is expressed as “the rate of change of the angular momentum of a body is equal to the net torque acting it.” For a non-rigid body with zero net torque, the angular momentum remains constant, but the angular velocity changes in accordance with Iω = constant where I is the moment of inertia of the body. 6-5C No. Two rigid bodies having the same mass and angular speed will have different angular momentums unless they also have the same moment of inertia I. Linear Momentum Equation 6-6C The relationship between the time rates of change of an extensive property for a system and for a control volume is expressed by the Reynolds transport theorem, which provides the link between the r system and control volume concepts. The linear momentum equation is obtained by setting b = V and thus r B =