Mechanics Flashcards
What is a vector?
A quantity with both direction and magnitude
What is a scalar?
A quantity with just direction
What must be true of the 3 forces on a particle in order for it to be in equilibrium?
They must form a closed vector triangle
Define moment
Force x perpendicular distance between the line of action of the force and the point
What is the principle of moments?
For a system in equilibrium, the sum of clockwise moments must equal the sum of the anti-clockwise moments, about a given point
What is a couple?
A pair of equal but oposite forces acting on a body, but not along the same line
What are the 2 conditions for an object to be in equilibrium?
-No net force
-No net moment
What is meant by the centre of mass of an object?
The single point on an object you can consider all the mass to act through
What is newtons 1st law?
Objects remain at a constant velocity unless acted on by a resultant force
What is newtons 2nd law?
F=ma
What is newtons 3rd law?
If object A enters a force on object B, then object B will exert an equal by opposite force on object A
How is drag linked to velocity?
Drag is proportional to V^2
If there is no air resistance, what happens to the horizontal component of velocity in projectile motion?
It remains constant
What is the principle of conservation of linear momentum?
Total momentum before a collision = total momentum after a collision, provided no external forces act
What conditions need to be met for momentum to be conserved?
No external forces act on the particle
What is an elastic collision?
Kinetic energy and momentum are conserved
What is an inelastic collision?
Kinetic energy is not conserved, but momentum is
How is force linked to momentum?
Force = change in momentum/time
What is given by the area under a force time graph?
Change in momentum (or impulse)
Define work done
Force x distance moved in the direction of the force
What is the principle of conservation of energy?
Energy cannot be created or destroyed, only transferred from one store to another
What is lift?
The upwards force perpendicular to fluid flow
What’s the area of a force-displacement graph?
Work done
