Section 4 Mechanics Flashcards
What is a scalar quantity
A quantity with only magnitude
What is a vector quantity
A quantity that has a direction and magnitude
How do you add vectors ( not a scale drawing)
Vectors are added in vertical and horizontal components
How to use a scale drawing with vectors
Use a scale appropriate for the size of vectors: pay attention to angles and directions
Resolving vectors: how ?
Use either vertical or horizontal components for perpendicular forces, use the parallelogram method , or split each forces into their vertical and horizontal components
Newton’s first law
If an object is at rest, and no other force acts upon it then the object will remain at rest. An object in motion remains in motion until acted upon by another force.
Newton’s second law
*F=ma
* rate of change of the momentum of a body is equal in both magnitude and direction to the force imposed on it
Newton’s third law
- for every action there is an equal and opposite reaction
- if object A acts a force upon object B, then object B will exert an opposite yet equal force upon object A
What is equilibrium
Forces are balanced in equal and opposite directions, there is no resultant force
How to work out moments
Force x perpendicular distance about the point
What is a couple ( moments )
- a pair of equal parallel forces pointing in opposite directions
Explain the principle of moments
- when a body is balanced, the total clockwise moment about a point equals the total anticlockwise moment about the same point.
*Moment =force F x perpendicular distance from the pivot d.
Centre of mass
Point at which the weight force acts upon an object
Define speed
How fast something is moving, regardless of direction
Define displacement
How far an objects travelled from it’s starting point in a given direction
Define velocity
The rate of change of an objects displacement
Define acceleration
The rate of change of an objects velocity
What is the gradient on a displacement
The velocity of the object
How do you find the velocity of an object at one point
By drawing a tangent at the point in intrest
What does a curve represent on a displacement time graph
Acceleration or deceleration
How would you find the average velocity on a displacement time graph
The total change in displacement divided by the total time taken
A line becomes steeper on a velocity time graph, what does this mean
A greater accleration
What does the area under a velocity time graph represent
Displacement
What does a straight line represent on a velocity time graph
Uniform acceleration
What does a curved line represent on a velocity
Non uniform acceleration
What does the area under an acceleration time graph represent
Total change in velocity
Define Newton’s first law
The velocity of an object will not change unless a resultant force acts on it
Define Newton’s second law
The acceleration of an object is directly related to the net force and inversely related to it’s mass
Define Newton’s 3rd law
If an object A exerts a force on object B, then object B exerts an equal but opposite force on object A
