2.2.2 Mechanics - Kinetics Flashcards
What are the equations for
s = distance travelled around an arc of a circle
v = angular velocity
a = angular acceleration
R = radius
theta = angle of arc in radians
Note: These equations always result in radians
Also note: angular part eg angular velocity acceleration is on far right and needs manipulation
1/6 rad/s , 5(pi) rev/min
1/160(pi) rev/s^2
89,000 ft
What is the formula for the period T of a pendulum
What is the formula for Time Period T and consequently for f frequency?
What is simple harmonic motion (shm)?
If we consider only the horizontal motion of the mass and neglect its vertical motion as it swings (an assumption which can be made if the string is long compared to the amplitude of swing), then the periodic motion is said to be simple harmonic motion
In terms of a pendulum;
If the displacement of the mass is plotted as a function of time, it will trace out a pure _____ wave
sine
Frequency is measured in:
The number of cycles per second, f in hertz
formula: f = 1 /T where T is the time period
In terms of a pendulum:
When its velocity is zero, its acceleration is a _______and when its acceleration is zero, its velocity is _______
In terms of a pendulum:
When its velocity is zero, its acceleration is a maximum and when its acceleration is zero, its velocity is maximum
0.6 Hz, 16.8 seconds
also recall: frequency f = 1/T
What is the formula for Work
Work = (Force)(Distance)
Because of the constant presence of friction, the _____ work is always greater than the _____ work.
Some of the input work is not useful work but serves to produce sound energy (a squeek), light energy ( a spark) or heat energy
Because of the constant presence of friction, the input work is always greater than the output work.
Some of the input work is not useful work but serves to produce sound energy (a squeek), light energy ( a spark) or heat energy
The type of lever shown in the picture is a First/Second/Third class lever?
First class lever: The fulcrum is between the load and the applied force.
The type of lever shown in the picture is a First/Second/Third class lever?
Second class: The load is between the fulcrum and the applied force.
(remember: second class citizens are scum and load their bags on the plane not caring)
The type of lever shown in the picture is a First/Second/Third class lever?
Third class: The applied force is between the load and the fulcrum.
(Remember: 3rd world countries put a lot of effort in but are still poor despite their efforts)
In a system of pulleys, how would you find the mechanical advantage?
Count the number of ropes excluding the force bit of the rope and that is your mechanical advantage of that system.
What is the Ideal Mechanical Advantage formula for a wheel and axle
where r is the radius of the axle
and R is the radius of the wheel
What is the Ideal Mechanical Advantage formula of an inclined plane?
where theta = angle of inclined plane
The screw jack is a development of the _____________
What is the formula for the Ideal Mechanical Advantage of a screw jack?
inclined plane
where p is the pitch of the screw (distance between adjacent threads)
and r is the radius of the turn
3
3
71%
Efficiency = AMA / IMA
80%
Efficiency = Wo / Wi
(Efficiency also = AMA / IMA)
33.3 lbs
Recall that:
Wheel and axle IMA = R/r (R=radius of wheel and r= radius of axle)
Efficiency = AMA /IMA
AMA = Fo / Fi
375 lbs
Recall:
Hydraulic jack ima = R2 / r2 (where R is radius of large piston and r is radius of small piston)
However question gives area already so really Hydraulic jack ima = large area/small area
Efficiency = AMA/IMA (also = Wo / Wi )
AMA = Fo / Fi
90.9%
IMA of a pulley system = number of strands
efficiency = AMA / IMA (= Wo / Wi )
AMA = Fo /Fi
Does the idler gear alter the velocity ratio?
The idler gear does not alter the overall Velocity Ratio
Velocity Ratio is (in terms of teeth on a gear)
What is the gear ratio?
Gear ratio = Product of number of teeth in driven gears / Product of number of teeth in driver gears
What is meant by concurrent forces?
Concurrent forces means that the forces all act at a single point
What is meant by non concurrent forces?
Non-concurrent means the forces do not act at a single point.
What is meant by Non concurrent coplanar
Non-concurrent coplanar means that the forces act in different lines but only on one plane, in other words two dimensions only.
There will be a resultant force and a resultant moment of force but only in the plane of the paper
