Topic 4 - Mechanics Flashcards
Acceleration
Change of velocity per unit time.
Acceleration of free fall
Acceleration of an object acted on only by the force of gravity.
Braking distance
The distance travelled by a vehicle in the time taken to stop it.
Centre of Mass
The centre of mass of a body is the point through which a single force on the body has no turning effect.
Couple
Pair of equal and opposite forces acting on a body but not along the same line.
Displacement
Distance in a given direction
Drag force
The force of fluid resistance on a object moving through the fluid.
Efficiency
The ratio of useful energy transferred (or the useful work done) by a machine or device to the energy supplied to it. The ratio of the machines outward power to its input power.
Effort
The force applied to a machine to make it move.
Equilibrium
State of an object when at rest or in uniform motion.
Force
Any interaction that can change the velocity of an object. measured in Newtons.
Free body force diagram
A diagram of an object showing only the forces acting on the object.
Friction
Force opposing the motion of a surface that moves or tries to move across another surface.
Gravitational field strength
Force of gravity per unit mass on a small object.
Inertia
Resistance of an object to change of its motion.
Kinetic energy
The energy of an object due to its motion.
Load
The force to be overcome by a machine when it shifts or raises an object.
Mass
Measure of the inertia or resistance to change of motion of an object.
Moment of a force about a point
Force x perpendicular distance from the line of action of the force to the point.
Momentum
Mass x velocity
Motive force
The force that drives a vehicle.
Newton’s first law of motion
An object remains at rest or in uniform motion unless acted on by a resultant force.
Newton’s second law of motion
The rate of change of momentum of an object is proportional to the resultant force (F) on it. Newton’s second law may be written as F = change in (ma)/ change in time. For constant mass, this equation becomes F = ma.
Potential energy
The energy of an object due to its position.
Power
Rate of transfer of energy.
Pressure
Force per unit area acting on a surface perpendicular to the surface.
Principle of conservation of energy.
Energy cannot be created or destroyed.
Principle of moments
For an object in equilibrium, the sum of the clockwise moments about any point = the sum of the anti-clockwise moments about that point.
Projectile
A projected object in motion acted on only by the force of gravity.
Scalar
A physical quantity with magnitude only.
Speed
Change of distance per unit time. Measured in m/s
Stopping distance
Thinking distance + braking distance
Terminal speed
The maximum speed reached by an object when the drag on it is equal and opposite to the force causing the motion of the object.
Thinking distance
The distance travelled by a vehicle in the time it takes the driver to react.
Useful energy
Energy transferred to where it is wanted when it is wanted.
Vector
A physical quantity with a magnitude and direction.
Velocity
Change in displacement per unit time.
Weight
The force of gravity acting on an object.
Work
Force x distance moved in the direction of the force.
