Topic 2: Mechanics Flashcards
Define: displacement.
The distance in a given direction from a fixed origin. It is a vector quantity.
What is the symbol for displacement?
s
Define: velocity.
Velocity is the rate of change of displacement. It is a vector quantity.
Define: speed.
Speed is the rate of change of distance. It is a scalar quantity.
Define: acceleration.
The rate of change with time of the velocity vector. It is a vector quantity.
What is an instantaneous value of speed?
Speed at a particular moment in time
What is an instantaneous value of velocity?
Velocity at a particular moment in time
What is an instantaneous value of acceleration?
Acceleration at a particular moment in time
What is an average value of speed?
Speed over a period of time.
What is an average value of velocity?
Velocity over a period of time
What is an average value of acceleration?
Acceleration over a period of time
When is an object in free fall?
When an object is falling under the sole influence of gravity or the effects of air resistance are being ignored. In the absence of air resistance, all objects have the same acceleration of free-fall, independent of their mass.
What is terminal velocity?
The point by which the velocity of a falling object remains constant and acceleration is zero.
What effect does terminal velocity have on an object?
- At the start, the object accelerates downwards because of its weight. There is no air resistance. There is a resultant force acting downwards
- As it gains speed, the object’s weight stays the same, but the air resistance on it increases. There is a resultant force acting downwards.
- Eventually, the object’s weight is balanced by the air resistance. There is no resultant force and the object reaches a steady speed, called the terminal velocity.
Define: force.
The cause of a deformation or a velocity change. A force is a vector quantity.
Define: weight.
Gravitational force. The force between objects as a result of their masses.
Define: drag
Forces that oppose the motion of a body through a fluid. They are directed opposite to the velocity of the body and generally depend on the speed of that body.
What effect does a higher speed have on drag force?
Higher speed equals higher drag force.
When will an object experience upthrust?
When it is in a fluid medium.
When will an object float?
When the upthrust force is equal to the weight.
Define: frictional forces.
Forces that oppose the motion of a body.
What does Hooke’s law state?
Up to the elastic limit, the extension, x of a spring is proportional to the tension force, F. The constant of proportionality k is called the spring constant.
Define: resultant force.
The overall force acting on an object when all the individual forces acting on that object have been added together.
State Newton’s First Law of Motion.
An object continues in uniform motion in a straight line or at rest unless a resultant external force acts.