Mechanics Flashcards
What is a vector?
A quantity with direction as well as magnitude
What is scalar?
A quantity with only magnitude (no direction)
What must be true of the 3 force vectors acting on a particle in order for the particle 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 the clockwise moments is equal to the sum of the anti-clockwise moments, about any given point
What is a couple?
A pair of equal and opposite 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 and no net moment
What is meant by the centre of mass of an object?
The single point that you can consider all the weight of the object to act through
Newtons First law ?
Objects remain at constant velocity unless acted on by a resultant force
Newtons Second law?
Force= mass x acceleration
Newton’s third law
If an object A exerts a force on object B, then object B exerts an equal but 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 the conservation of linear momentum?
Total momentum before a collision= total momentum after the collision, provided no external forces act
What condition needs to be met for momentum to be conserved?
No external forces act on the particles
What is an elastic collision?
Kinetic energy is conserved
And momentum is conserved
What is an inelastic collision?
Kinetic energy is not conserved
But momentum is conserved
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
Define work done
Force x distance moved in the direction of the force
What is the principle of the conservation of energy?
Energy can never be created nor destroyed
It can only be transferred from one form to another
How do you calculate the moment of a couple ?
One of the forces X perpendicular distance between the lines of action of the forces
How do you calculate the change in momentum?
Mv-Mu
What is the equation for workdone when the force is parallel to the direction of motion?
Force X distance
