Physics 1: Kinematics, Energy, Momentum, Work Flashcards
Forces are vectors required to change _____ and can be caused by any push or pull.
velocity
Examples of push/pull forces used to change velocity
Gravity
Friction
Rotation
_____, like Forces, are vectors that can cause a change in velocity. Net ____ must be equal to 0 to maintain equilibrium.
Torques
Forces that act over a distance
Represents a change in energy
work
May be converted from kinetic to potential and back but total value must always be conserved
energy
even if some energy is lost to the environment, _____ is always conserved in collisions
momentum
VAT Kinematic Equation
Vf = Vo + a*t
VAX Kinematic Equation
Vf^2 = Vo^2 + 2ax
VTAX Kinematic Equation
x = Vo * t + 1/2 * a * t^2
Uniform Acceleration Equation
x = 1/2 (Vo + Vf) * t
Equation: When PE completely converted to KE
V^2 = 2gh
Definition: Newton’s First Law
Inertia
an object in motion (or at rest) will stay in motion (or at rest) unless acted on by a net outside force
Definition: Newton’s Second Law
To change velocity, you need a Force, which produced acceleration
When does acceleration = 0?
when an object is not moving
when velocity is constant
SI Unit: Force
Newtons = kg*m/sec^2
A falling object accelerating due to gravity will encounter air resistance _________ to its increasing velocity
proportional
At terminal velocity, the air resistance equals _______, resulting in no Fnet and no acceleration
force of gravity
Definition: Newton’s Third Law
Every action has an equal and opposite reaction
Force pairs must be the same TYPE of force (i.e. Gravity, Normal Force)
Newton’s Third Law only applies to gravity when?
If you enlarge the system to include to include the source of gravity, i.e. the Earth itself
The force exerted by a surface that opposes
acts perpendicular to the surface
Normal Force
If F(net) = 0, and the only other force acting on the object is gravity, then the magnitude of the normal force (Fn) = ?
F(g) = m*g
*Note: g = accel due to gravity= ~10 m/s^2
If an elevator is accelerating upward, F(n) also includes opposition to the force of upward acceleration (m*a), so F(n) = ?
F(n) = ma + mg
If an elevator is accelerating downward, F(n) = ?
F(n) = ma - mg
A weight scale measures ______
the normal force
tendency of objects to stick together, opposing new forces
opposes movement
Friction
type of friction between two objects that are sitting still
varies w/ the force applied
has an absolute maximum, after which motion occurs and this value drops to zero
static friction
type of friction between moving objects
proportional ONLY to the Normal force, not the force applied
kinetic friction
tendency of masses to attract other masses
force is always attractive
gravity
Equation: Force due to gravity
F(g) = G m1 * M2 / r^2 = mg
Note: G-gravitational constant; g = accel due to g; M-mass of earth; m-mass of object; r-radius of Earth from center to surface
sin(0)
= 0 (square root 0/2)
sin(30)
= 1/2 (square root of 1/2)
sin(45)
= square root of 2/2
sin(60)
= square root of 3/2
sin(90)
= 1 (square root of 4/2)
sin(180)
= 0
sin(270)
= -1
cos(0)
= 1 (square root of 4/2)
cos(30)
= square root of 3/2
cos(45)
= square root of 2/2
cos(60)
= 1/2 (square root of 1/2)
cos(90)
= 0 (square root of 0/2)
cos(180)
= -1
cos(270)
= 0
Equation: Force of gravity in x-direction on inclined plane
F(g)x = mgsin(theta)
Equation: Force of gravity in the y-direction on inclined plane
F(g)y = mgcos(theta)
What opposes the force of gravity in the x-direction on an inclined plane?
Tension
Friction
What opposes the force of gravity in the y-direction on an inclined plane?
Normal force
Equation: Centripetal Force
F(c) = (m * v^2) / r
Equation: Centripetal Acceleration
a(c) = v^2 / r
Note: Centripetal Force on a satellite is caused by gravity. Since F = m*a, a=v^2/r (from Centripetal force equation)
Equation: Torque at equilibrium
d1 * m1 * g * sin(theta1) = d2 * m2 * g * sin(theta2)
transfer of energy by a force acting over a distance
change in energy
SI Unit: Joule = Nm = (kgm^2)/sec^2
work
If the force applied to a system is ________ to its motion, no work is done.
perpendicular
Why is no work done when a force acts perpendicularly to an object’s motion?
cos(90) = 0
LOSS of E to the surroundings is ______ work being done BY the system and ______ work being done ON the system
positive work done by the system
negative work done on the system
GAIN of E from the surroundings is _______ work being done BY the system and ________ work being done ON the system
negative work done BY the system
positive work done ON the system
ability to do work
scalar
measured in Joules
Energy
Equation: Kinetic Energy
K.E. = 1/2mv^2
Equation: Gravitational Potential Energy
U = mgh
Equation: Work-Energy Theorum
Work(net) = change in Kinetic Energy
F*d = 1/2 mv^2
Note: d = DISPLACEMENT
2 instances where the net work = 0
- force applied is perpendicular to velocity: cos(90) = 0
2. no change in position (displacement = 0)
3 examples of conservative forces
electrostatic
gravity
spring
forces that are path independent
state functions that only depend on initial state and final state
conservative forces
forces that are path dependent
vary depending on what happens between states
nonconservative forces
4 examples of nonconservative forces
air resistance
turbulence
friction
viscosity
measures energy expenditure over time
increases when max value occurs over shortest amount of time
SI unit = Watt = Joule / sec
power
an objects tendency to keep moving
vector quantity w/ magnitude and direction
SI unit = kg*m/sec
momentum
Equation: momentum
momentum = m*v
For all types of collisions, ________ is ALWAYS conserved
momentum
Equation: Conservation of momentum
m1v1i + m2v2i = m1v1f + m2v2f
During an __________, energy is lost due to friction, sound, light, configuration changes, etc.
inelastic collision
In an ______, energy is lost and objects stick together.
totally inelastic collision
Equation: Conservation of momentum in totally inelastic collision
m1v1i + m2v2i = (m1+m2) * vf
Elastic collisions lead to final velocities of hte _____ magnitude and ______ direction
same magnitude
final direction
Equation: conservation of momentum due to inelastic collision
1/2 * m1v1i^2 + 1/2 * m2v2i^2 > 1/2 *m1 * v1f^2 + 1/2 * m2v2f^2
how fast momentum of an object changes
increasing time decreases Force
Impulse
