Mechanics and Materials Flashcards
Examples of scalar quantities
Direction, speed, mass, work, energy, time
Examples of vector quantities
Displacement, velocity, acceleration, force
Conditions for equilibrium
Resultant force= 0N
Principle of moments applies about any point on the body ( no resultant moment)
Torque/ total moment of a couple
T = F s
F= magnitude of one of the forces s = perpendicular distance between the forces
Stable
Low centre of mass
Wide base
Unstable
High centre of mass
Small base
Distance time graphs
Gradient = speed
Straight line, constant gradient = constant speed
Flat line = stopped
Velocity time graph
Gradient = acceleration
Flat line = constant speed
Area under graph = distance travelled
Suvat equations
V = u + at
S = 1/2 (u + v) t
S = ut + 1/2a t^2
V^2= u^2 +2as
Projectile motion ignoring drag
Parabola
Constant horizontal speed (a=0)
Constant vertical acceleration (a=9.81 ms^-2)
Projectile motion introducing air resistance
Max height reduced Reduced range Causes deceleration Flight path no longer symmetrical (descent steeper than ascent) Top of curve shifts left
Newton’s first law
An object moves with uniform motion unless acted on by a resultant force.
Newton’s second law
F = ma
F = resultant force/N m = mass/kg a = acceleration in direction of force /ms^-2
Notes for Newton’s third law
2 forces, same size, same type, along same line, different bodies, opposite directions
Work done by spring (while Hooke’s law is obeyed)
Area under graph
1/2 Fx
1/2 k x^2
