Mechanics Flashcards
Define a scalar quantity
Scalar quantitys have magnitude only. They do not have direction. E.g. speed, time
Define a vector quantity
Vector quantitys have both magnitude and direction. E.g. acceleration, displacment
How must vector be added?
Force arrows drawn tip to tale
Define coplanar
If forces are coplanar they act in the same direction
Define equlibrium
if the forces on a body are in equlibrium it means the resultant force is zero
Give the conditions for forces to be in equlibrium
If coplanar forces act on an object, the object is in equlibrium if the forces form a closed shape when added tip to tail on a force vector diagram
what is the weight (W) force?
Force due to gravity that acts towards the center of the earth
What is the frictional (F) force?
Acts between two surfaces in contact, opporsite to the direction of motion
What is air resistance/ drag?
Acts on an object moving through air due to collision of particles, in the opporsite direction to motion
what are the normal contact/reaction (R) forces?
Foreces that act on an object in contact with a surface, acts perpindicular to the surface.
What is tension (T)?
A force that streches an object
What is boyancy/upthrust?
A force which acts upwards on an object partialy or fully submerged in a fluid
What is the driving force (D)?
A force produced by and engine
What are the rules for free body force diagrams?
> Draw a point in the center of mass of the body
Draw the body free from contact with any other object
Draw the forces acting on the body using vectors
Label the forces approprietly
Give the equation for a moment
moment=Fd
Define a moment
A mesure of the turning affect of a force. It is a vector quantity.
Give the principal of moments
For a system to be in equlibrium, the sum of clockwise moments about a point must be equal to the sum of the anitclockwise momesnts (about the same point).
What are the equations for resolving a force not perpindicular to a point?
M=Fxdsinθ M=Fsinθxd
What are the moments of a couple?
A couple is a pair of forces of equal size which acts parallel to each other but in opporsite directions.
> the forces are coplanar
> they do not cause any resultant linear force
> cause rotational movement
What is the equation for the moment of a couple?
Moment of a couple=size of obe of the force X perpindicular distance between the line of action of the force
Define center of mass
The center of mass of an object is the singular point that you can consider the whole weight to act through.
What is stability?
How stable an boject is depends on its center of mass and base area.
> the lower the center of mass the more stable the object
> the wider the base area the more stabe the object
