Dynamics Flashcards
(22 cards)
What is kinematics?
Study of the geometry of motion alone.
What is kinetics?
Study of the unbalanced forces that act to alter the motion.
What is the kinetics of particles?
When all of the applied forces are concurrent through the centre of mass, there will be no rotation and the object may be treated as a particle.
What is mass?
a measure of an object’s reluctance to accelerate
What is the direct application of Newton II?
Since a particle will accelerate only in the direction of the unbalanced applied force, we may apply the law separately in each orthogonal component direction (x,y or n,t) as they will not interact.
What is momentum?
the unbalanced force equals the rate of change of momentum.
What is the work energy method?
Only the tangential force component (n-t coordinates) does work on a particle.
What is a conservative force?
The work done by a weight force is independent of the path taken
What is gravitational potential energy?
The gravitational potential energy of a particle of mass m is the negative of the work done against the gravitational field to elevate the particle a distance h above some arbitrary reference plane
What is elastic potential energy?
Elastic potential energy is stored within an elastic element, such as a spring, when work is done on that spring by either an extension or compression force. The work may be recovered during the spring’s release. The elastic force is a conservative force.
What is the law of conservation of dynamical energy?
Where the only forces are elastic, gravitational and “non-working” constraint forces, the term U will be zero and the energy expression becomes ∆E = 0 , which is the law of conservation of dynamical energy.
What is rectilinear translation?
every point on the body moves in parallel straight lines, nor does any line attached to the object rotate. Describing the kinematics of any point on the object completely defines the motion of every point.
What is curvilinear translation?
every point on the body moves on congruent curves, and any line attached to the object does not rotate. Describing the kinematics of any point on the object completely defines the motion of every point.
What is fixed axis rotation?
every point on the body moves on a circular path about a fixed axis. The angular motion kinematic equations are analogous to those of rectilinear motion. Angular displacement = θ in radians.
What is the General Plane Motion?
the object executes a combination of translation and rotation. All lines on a rigid object, lying in its plane of motion, have the same ∆θ, ω and α.
What is the mass centre? (3)
When the line of action of an unbalanced force acts through the mass centre, translational acceleration only will result, i.e. no rotational acceleration.
Alternatively, the mass centre is that point about which an object will rotate when subject to a (pure) applied couple. i.e. the mass centre will remain stationary while all other points orbit about it with circular motion.
For translational acceleration purposes, all of the mass may be considered to be concentrated at the mass centre, often designated as G.
What is a moment of inertia?
is a measure of reluctance of an object to accelerate angularly. It is dependent on the distribution of mass about the axis of rotation
What is the significance of the centred area of the beam’s cross section?
centroid area is a neutral axis (strain from bending is 0)
What is the significance of the second moment of area of the beam’s cross section about the neutral axis?
A beam’s resistance to bending is related to I
What is the difference between gauge pressure and absolute pressure?
absolute pressure is = gauge pressure + atmospheric pressure
Explain why the bottom of the submarine experiences a force and state in which direction it acts.
Pressure at a point acts in all directions within a fluid and perpendicular with any solid surface in contact with the fluid.
Why is there a force experienced by the pipe bend? (2)
pipe applies force to change direction of fluid
must be an equal or opposite reaction of force on the pipe
