Mechanics definitions Flashcards
Scalar
A quantity that has a magnitude and no direction.
Vector
A quantity that has both a magnitude and a direction.
Displacement
Distance from a fixed point in a given direction.
Velocity
Rate of change of displacement
Acceleration
Rate of change of velocity
Centre of gravity
The point at which the force due to gravity acts on an object. The object can be treated as though its total mass is concentrated at this point.
Newton’s first law
An object remains at rest or at constant velocity unless acted on by an external resultant force
Newton’s second law
When an object is acted on by an external resultant force it accelerates in the direction of the resultant force. The magnitude of the acceleration is proportional to the magnitude of the force and inversely proportional to the mass of the object. (F=ma)
Newton’s third law
If body A exerts a force on body B, body B exerts an equal and opposite force on body A.
Moment about a point
Force multiplied by perpendicular distance between the line of action of the force and the point.
Principle of moments
If an object is in equilibrium the sum of the clockwise moments about a point is equal to the sum of the anticlockwise moments.
Momentum
Mass multiplied by velocity.
Elastic collision
A collision in which kinetic energy is conserved.
Work done
Distance multiplied by component of force I the direction of the motion.
Power
Energy transferred per second (work done per second).
