Modules 3 Definitions Flashcards
Acceleration
The rate of change of velocity
Average Speed
Distance over time for the entire region of interest
Braking distance
The distance travelled between the brakes being applied and the vehicle coming to a stop.
Displacement
The direct distance between and object’s starting and ending positions. It is a vector quantity and so has both a direction and a magnitude.
Displacement-Time graphs
Plots showing how displacement changes over a period of time. The gradient gives the velocity. Curved lines represent acceleration.
Free-fall
An object is said to be in free fall when the only force acting on it is the force of gravity
Instantaneous speed
The exact speed of an object at a specific given point.
Projectile motion
The motion of an object that is fired from a point and then upon which only gravity acts. When solving projectile motion problems, it is useful to split the motion into horizontal and vertical components.
Reaction time
The time taken to process a stimulus and trigger a response to it. It is affected by alcohol, drugs and tiredness.
Stopping distance
The sum of thinking distances and braking distance for a driven vehicle.
Thinking distance
The distance travelled in the time it takes for the driver to react. It is affected by alcohol, drugs and tiredness.
Velocity-time graphs
Plots showing how velocity changes over a period of time. The gradient gives acceleration. |Curved lines represent changing acceleration.
Velocity
The rate of change of displacement. It is a vector quantity and so has both a direction and a magnitude.
Archimedes’ Principle
The upwards force acting of an object submerged in a fluid, is equal to the weight of the fluid it displaces.
Centre of Gravity
The single point through which the object’s weight can be said to act.
Centre of mass
The single point through which all the mass of an object can be said to act
Couple
Two equal and opposite parallel forces that act on an object through different lines of action. It has the effect of causing a rotation without translation.
Density
The mass per unit volume of a material.
Drag
The frictional force that an object experiences when moving through a fluid.
Equilibrium
For an object to be in equilibrium, both the resultant force and resultant moment acting on the object must be equal to 0.
Free-body diagram
A diagram showing all the forces acting on an object. It is a good starting point to any mechanics problem.
Friction
The resistive force produced when there is relative movement between two surfaces.
Moment of force
The product of a force and the perpendicular distance from the line of action of the force to the pivot.
Newton
The unit of force
Newton’s Second Law
The sum of the forces acting on an object is equal to the rate of change of momentum of the object. It is also expressed as the net force acting on an object equalling the product of the object’s mass and acceleration.