Mechanics And Materials Flashcards
What is a vector?
Any physical quantity that has a direction as well as magnitude
What is a scalar?
Any physical quantity that is not directional
What is equilibrium?
An object is in equilibrium if it has a resultant force of zero and so it is not accelerating.
How do we know if forces are in equilibrium?
- We can construct a closed triangle of forces
- One of the forces is equal but opposite in direction to the sum of the other two
What is a free body diagram?
A diagram showing all forces that act on a point object.
What is a moment?
A moment of a force about any point=
Force x Perpendicular distance from the line of action of the force to the pivot
What is the principle of moments?
The sum of clockwise moments = the sum of anticlockwise moments
What is the centre of mass?
The centre of mass of a body is the point through which a single force on the body has no turning effect.
What is a couple?
A couple is a pair of equal and opposite forces acting on a body, but not along the same line of action. The couple tries to turn the body.
How do you calculate the moment of a couple?
Force x Perpendicular distance between the lines of action of the forces
What is a stable equilibrium?
A body is in stable equilibrium if it is displaced then released and returns to the equilibrium position.
What is an unstable equilibrium?
A body is in unstable equilibrium if it is slightly displaced from equilibrium it accelerates away from its equilibrium
When does a body tilt?
Fd>Wb/2
Why does the force required to tilt an object decrease as it becomes more tilted?
Because the width of the base decreases
When will an object topple?
When the line of action of the weight of the object is pushed past the pivot
