Mechanics & Materials Flashcards
Balanced forces:
If two equal and opposite forces are acting on an object, it is said to be in…
A:
Equilibrium
Moments:
Explain what a moment is.
A:
the moment of a force about any point is defined as the force x the perpendicular distance from the line of action of the force to the point.
Moments:
state the principle of moments.
A:
sum of the clockwise moments is equal to the sum of the anti-clockwise moments .
Moments:
Equation for the principle of moments is…
A:
F1 d1 = F2 d2 +…
Because the force is weight and are both measured in Newtons, N.
Moments:
What is a couple?
A:
a pair of equal and opposite forces acting on a body, but not along the same line.
Stability:
What is stable equilibrium?
A:
If a body is displaced then released, it returns to its equilibrium position
Newton’s Laws of Motion:
state Newton’s first law.
A:
Objects either stay at rest or move with constant velocity unless acted on by a force
Newton’s Laws of Motion:
state Newton’s second law.
A:
the rate of change of momentum of an object is proportional to the resultant force on it.
f is proportional to ma
f=ma
Forces and Acceleration:
what is inertia?
A:
resistance to change of motion.
Impulse:
define impulse.
A:
force x the time n which the force acts.
Momentum:
what is the principle of momentum.
A:
The principle of conservation of momentum is that the total momentum will remain constant, provided that no external forces act upon the system.
Momentum:
will momentum of a secondary object due to the impact force from the primary object be positive or negative?
A:
During a collision, the objects both exert an equal and opposite force on each other when they are in contact.
Therefore if one object loses momentum the other will gain momentum equal to the change so the value can be either.
Collisions:
What is the difference between an elastic and inelastic collision?
A:
Within an elastic collision, there’s no loss of Kinetic Energy (Ek) whereas in a inelastic collision, there is less kinetic energy after the collision that before as some of the energy is lost to the surroundings that can be in another form such as thermal, sound etc.
Moments:
What a single support force?
A:
When an object is in equilibrium at one point only, the support force is equal and opposite to the total downwards force that is acting on the object.
Moments:
What is a double support force equal to?
A:
If the COM (Centre of Mass) of a beam or uniform mass is midday between 2 pillars then the weight of the object is shared equally between both pillars.
This means that each pillar is equal to half of the weight.
Meaning that the support force for the left pillar if we take that to be pillar X, will be equal to the overall weight, W, x by the distance from the pillar X and the COM to be dX divided by the distance from one pillar to the other which would be D.
SX = WdX / D
This is the same for the other pillar which could be pillar Y or pillar Z etc.
Remember to subscript.
