Physics A.2 Forces and Momentum

Term: Linear momentum

Definition: Linear momentum is a vector quantity defined as the product of an object’s mass and its velocity. It is given by p = mv, where m is the mass and v is the velocity of the object.

Term: Impulse

Definition: Impulse is the change in momentum of an object. It is given by J = FΔt, where F is the average force acting on the object and Δt is the time over which the force acts.

Term: Elastic collision

Definition: An elastic collision is a collision in which both momentum and kinetic energy are conserved. The total kinetic energy before the collision is equal to the total kinetic energy after the collision.

Term: Inelastic collision

Definition: An inelastic collision is a collision in which momentum is conserved but kinetic energy is not. Some of the kinetic energy is transformed into other forms of energy, such as heat or sound.

Term: Explosion

Definition: An explosion is a process in which a system breaks apart into multiple parts, typically releasing energy. In an explosion, the total momentum before the explosion is zero, and the total momentum after the explosion is also zero.

Term: Centripetal acceleration

Definition: Centripetal acceleration is the acceleration experienced by an object moving in a circular path, directed radially inward toward the center of the circle. It is given by a = v²/r = ω²r = (4π²r)/T², where v is the tangential velocity, r is the radius of the circle, ω is the angular velocity, and T is the period of the motion.

Term: Newton’s 1st law of motion

Definition: An object at rest stays at rest and an object in motion stays in motion with a constant velocity unless acted upon by a net force.

Term: Newton’s 2nd law of motion

Definition: The net force acting on an object is equal to the mass of the object multiplied by its acceleration (F = ma). The net force is the rate of change of momentum.

Term: Newton’s 3rd law of motion

Definition: For every force acting on A by B, there is an equal magnitude and opposite direction of force acting on B by A.

Term: Force

Definition: Force is a vector quantity that can change the state of motion of an object. It is measured in Newtons (N) and is given by the equation F = ma, where m is mass and a is acceleration.

Term: Free-body diagram

Definition: A free-body diagram is a graphical representation used to visualize the forces acting on a single object. It isolates the object and shows all the forces as vectors drawn from the object’s center of mass.

Term: Resultant force

Definition: Resultant force is the net force acting on an object, calculated by vectorially summing all the individual forces acting on the object. It determines the acceleration of the object according to Newton’s second law (F = ma).

Term: Normal force

Definition: The normal force is a contact force that acts perpendicular to the surface of contact and prevents objects from passing through each other. It is typically equal in magnitude but opposite in direction to the weight of an object resting on a surface.

Term: Frictional force

Definition: Frictional force is a contact force that acts parallel to the surface of contact and opposes the relative motion or tendency of motion between two surfaces in contact. It is given by Ff ≤ μs FN for static friction and Ff = μd FN for kinetic friction, where μs and μd are the coefficients of static and dynamic friction, respectively, and FN is the normal force.

Term: Elastic restoring force

Definition: Elastic restoring force is a force that acts to restore a deformed elastic object to its original shape. It follows Hooke’s law, given by FH = -kx, where k is the spring constant and x is the displacement from the equilibrium position.

Term: Viscous drag force

Definition: Viscous drag force is a force that opposes the motion of an object through a fluid. It is given by Fd = 6πηrv, where η is the fluid viscosity, r is the radius of the object, and v is the velocity of the object through the fluid.

Term: Buoyancy

Definition: Buoyancy is an upward force exerted on an object immersed in a fluid, resulting from the displacement of the fluid. It is given by Fb = ρVg, where ρ is the density of the fluid, V is the volume of the displaced fluid, and g is the acceleration due to gravity.

Term: Magnetic force

Definition: Magnetic force is the force experienced by a moving charge or a current-carrying conductor in a magnetic field.