Mechanics and material Flashcards
What is the moment of of force about a point?
The force x the perpendicular distance from the line of action of the force to the point.
What is the principle of moments?
For an object in equilibrium, the sum of the clockwise moments about any point is equal to the sum of the anticlockwise moments about that point.
What is the centre of mass?
It is the point through which a single force on the body has no turning effect.
What is a couple?
Pair of equal and opposite coplanar forces acting on a body but not along the same line
What is a projectile?
An object in motion acted on only by the force of gravity.
Newton’s first law
An object remains at rest or in uniform motion unless acted on by a resultant force.
Newton’s second law
The rate of change of momentum of an object is proportional to the resultant force on it.
Inertia
Resistance of an object to change its motion
What is Newton’s third law?
When two objects interact they exert equal and opposite forces on each other
What is an inelastic collision?
When the colliding objects have less kinetic energy after the collision than before the collision.
What is energy?
The capacity to do work
What is kinetic energy?
The energy of an object due to its motion
What is potential energy?
The energy of an object due to its position.
Hooke’s law
The force needed to stretch a spring is directly proportional to the extension of the spring from its original length.
How to find the effective spring constant when two springs are in parallel
Add the two individual spring constants
How to find the effective spring constant when two springs are in series
1/k = 1/k1 + 1/k2
Elastic limit
The point beyond which a wire is permanently extended so will not return to its original dimensions when the force applied to it is removed.
How to calculate the elastic potential energy stored in a spring from a force against extension graph
The area under the graph
Define elasticity
Property of a solid that enables it to regain its shape after it has been deformed or distorted.
Define tensile stress
Force per unit area of cross-section in a solid perpendicular to the cross-section.
Define tensile strain
Extension per unit length of a solid when deformed
What is the Young’s modulus of a material?
Stress/strain (provided the limit of proportionality between extension and force hasn’t been exceeded. Used to measure the stiffness of a material.
What is the yield point of a wire?
The point at which the stress suddenly drops when the wire is subjected to increasing strain
Define plastic deformation
Deformation of a solid beyond it’s elastic limit