Kinematics and Dynamics Flashcards
What units make up the base units of the SI system?
length= meter mass=kilogram time= second current= ampere (=C/s) amt of substance = mole temperature = kelvin luminous intensity= candela (cd)
What are important derived units in the SI system?
force= newton = kgm/s^2
work and energy= joule= kgm^2/s^2
power= watt= kg*m^2/s^3
if the newton is the product of kilograms an dmetters/second^2, what units comprise the pound?
none it is a base unit in the imperial system. it is used for weight.
slug*ft/s^2
Which quantities are vectors and which are scalar?
vectors- displacement, velocity, acceleration, force
scalars- distance speed energy pressure and mass
How to do vector addition?
Add vectors tail to tip or break them into their componet vectors using sohcahtoa and pythag. theorem.
I needed a scalar quantity like work, how would i multiple the vectors?
by the dot product-
A(dot)B=abs(A)*abs(B) cos theta
the two vectors of interest would be force and displacement
If I need a third vector like torque, how would i multiple the org. vectors?
by cross product-
A x B=abs(A)*abs(B) sin theta
the two vectors of interest would be force an lever arm
displacement vs distance
displacement- vector quantity that connects the objects initial and final position
Distance- scalar quantity of the total distance traveled b the object
what is the relationship between instantaneous speed and velocity?
they are equal when considering the magnitude of the instantaneous velocity ( measure of the avg velocity as the change in time approaches zero)
velocity vs speed
velocity- vector whose magnitude is the rate of change of displacement in given time
speed- rate of distance traveled in a given time
What forces can act on an object by touching?
not touching?
force on touch- mechanical manipulation, friction
force no touch- gravity, electrostatics, magnetic, nuclear
If the r is doubled in the gravitational force eqn how will it affect F_g? tripling m_1?
2*r->F_g/4
3m_1->3F_g
What do you need to consider when calculating the static friction vector?
the coefficent of static fiction, the normal force on the object, and that friction always opposes an object’s motion
-stationary objects might not be experiencing a maximal static force of friction
when does kinetic friction come into play?
when an object begins sliding
a rolling object only means static
its also a constant value that depends on the coefficient of kinetic friction and the normal force but static can be from 0 to maximum
Where is the center of mass of an object?
the geometric center, only if the object is homogeneous ( in shape and density)
When no force is applied the velocity is…?
Constant, no force means no acceleration so the object must be at constant velocity
what can velocity vs time graphs tell you about acceleration?
a positive slope will tell you there is acceleration
a negative slope will tell you there is decelleration
What is the law of inertia?
first law-mass will be at rest or in motion at a constant velocity until a net force acts upon it
what is a move generalized way to look at the law of inertia?
second law-a net force must act upon an object for it to accelerate
Why do the moon and the earth have a balanced gravitational force on each other?
third law- for every application of force on an object, the object will apply an equal and opposite force back on the first
When air resistance is not negligible what happens to an object in free-fall
it will reach terminal velocity because the drag force from the air will eventually reach the same magnitude as the weight of the object and it will fall at a constant velocity.
What are four equations that relate acceleration, velocity and/or position? (regarding one dimensional motion)
v=v_0+at
x=v_0+(at^2/2)
v^2=v_0^2+2ax
x=v_constant*t
what relationships will you use to help solve projectile motion and inclined plane problems?
SOHCAHTOA
you’ll need to know the angle of trajectory or the angle of the inclined plane
why would an object discontinue motion in a circular path?
it exits when the centripetal force no longer acts upon it allowing the object to continue in a path tangential to the the circle at that point.
centripetal force eqn
F_c=(mv^2)/r
What basic concept can be useful when drawing free body diagrams?
breaking the forces into force components (trig) and then summing the ones in the same direction
to solve problems relating to translational equilibrium what concepts must you remember?
free-body diagrams and newtons three laws
What is torque
moment of force is generated by the application of force at some distance form the fulcrum
~t=r x F= r*Fsin theta
-~t= clockwise
+~t= counter clockwise
How to lift a heavy object with a lever
place the object close to the fulcrum and made the your downward force distance from the fulcrum much longer than the fulcrum distance to the object
