Unit 2 - Forces Flashcards
What 2 effects will a force have on a body?
Change its position in space
Deformation (to some degree - ignored in rigid body mechanics)
What is the difference between mass & weight?
Mass = quantity of matter in a body
Weight = force of gravity on a body (m x g)
How do you calculate density?
p = mass/vol
What does the amount of friction between two surfaces depend on?
Roughness, magnitude of force pushing them together, lubrication
Independent of surface area
How to calculate friction force?
F = µN
µ = coefficient of friction (measure of maximum friction force) N = force acting normally to surface
What are the 3 difference types of friction?
Static - exists only when motion is about to occur (once max friction force exceeded motion will being)
Sliding - exists only when sliding occurs between surfaces (sliding friction less than static)
Rolling - arises due to deformation of 2 surfaces by force acting normally when rolling (less than sliding friction)
Define pressure
F/A
when force acts perpendicularly to surface
What is meant by static equilibrium?
No resultant force (therefore at rest of constant velocity)
Sum of external forces = 0
Newton’s 3rd law?
To every action there is an equal and opposite reaction
Newton’s 1st law (of inertia)
Every body remains at rest or at a constant velocity unless acted upon by a resultant force
Inertia - tendency to do nothing or to remain unchanged (a body’s inertia is represented by its mass)
Newton’s 2nd law (of acceleration)
F = ma
Related to dynamic equilibrium when the sum of the external forces does not = 0
Equation for momentum?
p = mv
What is the principle of conversation of momentum?
The total momentum of a system is constant if there are no external forces acting
Equation for moments?
M = Fd
How do you calculate mechanical advantage?
MA = Effort arm/resistance arm
