Physics #1 Flashcards
base units
the standard units around which the system itself is designed
Ex: meter
derived units
associated base units with each other
Ex: Newton
what does the metric system use for length
meters
what is the imperial system?
the British system of measurements: foot, pound, second, mile
what are the units for energy/work (Joules)
(kg)(m^2)/(s^2)
what are the units for Power (watts)
(kg)(m^2)/(s^3)
what are the units for force (newtons)
(kg)(m)/(s^2)
what are Angstroms, nanometers
angstroms: 1 A = 10^-10 meters
nanometers: 1 nm = 10^-9 meters
what are the units for electron-Volts
1.6x10^-19 J
what are vectors?
vectors are numbers that have magnitude and direction
scalars
numbers that have magnitude only and no direction
vector or scalar: displacement
vector
vector or scalar: velocity
vector
vector or scalar: acceleration
vector
vector or scalar: force
vector
vector or scalar: distance
scalar
vector or scalar: speed
scalar
vector or scalar: energy
scalar
vector or scalar: pressure
scalar
vector or scalar: mass
scalar
compare distance and displacement for Earth orbit
the distance Earth travels is 940 million kilometers but its displacement is 0 (circular)
what is the resultant of two vectors
the sum or difference of two or more vectors
when multiplying a vector by a scalar, what will happen?
it’s magnitude will change but it will remain parallel or antiparallel to the original vector’s direction.
how is the idea of work tied into vectors?
Only need magnitude: dot product
work is Force (dot) displacement = |A||B|cos(theta)
how is the idea of torque tied into vectors?
Need both magnitude and direction: cross product
|A||B|sin(theta)
when do you use cross product vs. dot product?
dot product: just need magnitude of two vectors multiplied
cross product: need magnitude and direction of two vectors multiplied
RHR: first vector (thumb) x second vector (fingers) = resultant vector (palm)
the resultant of a cross product will always be _____ to the plane created by the two vectors
perpendicular
For cross product, does AxB = BxA?
no
for cross product, if a magnitude is negative, does it matter?
no, just goes into equation as the absolute value.
can the magnitude of a vector be negative?
no, it is the length of the vector which has no direction and thus is always positive.
displacement
an object in motion experiences a change in position in space
the displacement vector connects _____
in a straight line the objects initial and final positions.
does displacement or distance take into account the pathway taken?
distance
compare velocity and speed
velocity: displacement/time
speed: actual distance/time
True or false: the instantaneous speed of an object will always be equal to the magnitude of the object’s instantaneous velocity
true
True or false: the average speed of an object will always be equal to the magnitude of the object’s average velocity
false
every change in velocity is motivated by a _____
force
friction always ______ an object’s motion and cause it to slow down
oppose
when a car is driving, what type of friction is a tire experiencing?
static friction (the tire is not actually sliding on the road surface but rather it is rolling).
kinetic friction will always have a constant value regardless of ____ and _____
the surface area of contact or the velocity of the sliding object
is the coefficient of static friction greater than or less than that of kinetic friction?
greater
how does the mass of 1kg compare on the moon vs. Earth?
same
how does the weight of 1kg compare on the moon vs. Earth?
greater on Earth
when an object is thrown, the _____ travels in a simple parabolic pathway
center of mass
what is Newton’s First law of motion?
F = ma = 0
an object at rest or in motion with constant velocity will remain that way unless acted upon by a force
what is Newton’s second law of motion?
F = ma
an object of mass m will accelerate when the vector sum of the forces results in some nonzero resultant force vector.
what is Newton’s third law of motion?
F(ab) = -F(ba)
To every action, there is always an opposed but equal reaction
is Newton’s third law dependent on physical contact?
no, force of moon on Earth is same as force of Earth on the moon
free fall and kinematics
constant acceleration due to gravity, no air resistance, and does not reach terminal velocity.
when drag force is introduced to an object in free fall, what happens?
eventually, the object will speed up enough so that the drag force is equal to the weight of the ball and the ball will then fall with constant velocity according to Newton’s first law.
True or false: the time it takes an object to reach its max height is the same amount of time it takes to fall to its original height?
true
in uniform circular motion, the instantaneous velocity vector is always____ to the circular path
tangent
in uniform circular motion, what keeps an object from moving in a tangent to the circular motion and where does it point?
centripetal force
always points radially inward
In uniform circular motion, the tangential force is equal to _____
zero
at what angle will objects obtain the greatest vertical and horizontal displacement when launched?
vertical: 90 degrees (straight up)
horizontal: 45 degrees
because force is a vector, the resultant force is simply the ___ of the forces
sum
translational equilibrium exists when _____
the vector sum of all the forces acting on an object is 0.
the lever arm is _____
the distance between the applied force and the fulcrum
torques that generate clockwise rotation are considered ___
negative
in translational equilibrium, _____ is 0, while in rotational equilibrium, ____ is 0
net force
net torque
the coefficient of friction depends on _____
the two materials in contact
do falling objects with different mass have the same acceleration?
yes, gravity acceleration
is magnitude positive or negative?
always positive
The normal force and frictional force ______ as the angle of the incline increases.
decrease
