50.2 Aeroscience

50.2.2 Explain the meaning of:

(a) velocity

• Is the vector equivalent of speed. 
• It is distance travelled in a given direction in unit time.
• The term velocity is used, rather than speed, when the direction of travel is important.

(b) equilibrium

• An object in a state of rest or moving at a constant velocity is said to be in a state of Equilibrium.
• The sum of all the forces acting upon it is zero - no net force will exist to cause it to accelerate.
• Zero acceleration.

(c) momentum and

• The momentum of an object is the product of its mass and velocity - momentum = mv
• Momentum refers to the difficulty of stopping a moving object, or of changing its direction of travel.
• A large mass with low velocity can have the same momentum as a small mass with high velocity.
• Increased mass and/or velocity means an increase in momentum.
• Momentum is often confused with inertia - a stationary object with no velocity, has no momentum

(d) inertia.

• Is the tendency of an object to continue moving at a certain velocity or to remain at rest with no velocity.
• It is a property of, and depends solely on the mass of the object.
• A common definition of mass is that it is ‘the amount of matter in an object’.
• In the International System of units or SI system, mass is measured in kg’s.
• Mass and inertia cannot be separated - objects with a lot of mass have greater inertia than those with less mass.