Physics Midterm

When force is held constant…

mass and acceleration are inversely proportional (as mass increases, acceleration decreases) (as mass decreases, acceleration increases)

when mass is held constant…

force and acceleration are directly proportional (as one increases so does the other, as one decreases so does the other)

system

a collectin of interacting objects

area under the curve for a Force-Time graph

impulse = change in momentum

area under the curve for a Velocity-Time graph

displacement (vector)

determining direction of acceleration

when velocity and acceleration are same sign they are speeding up and when they are opposite the object is slowing down

constant velocity

0 = acceleration

position vs time graphs

positive slope means positive velocity which means positive direction. a straight line means velocity is constant and acceleration is 0. y-intercept is the starting position of the object

velocity vs time graphs

slope is acceleration, y-int = initial velocity, direction of motion is determined by y value, under the x axis is negative dir, straight line is consant velocity

ticker tapes

if the dots are getting farther apart the object is speeding up, if they are getting closer it is slowing down, and if they are the same the velocity is constant

free fall

acceleration due to gravity, no air resistence, a = g = -10m/s²

frictional force - F_f

a force caused by 2 surfaces sliding past eachother, friction opposes an object’s direction of motion

tension force - F_t

the force transmitted through a string, rope, cable, wire etc. it is directed along the length of the wire and pulls equally on the objects on the opposite ends of the wire.

spring force - F_spring

the force exerted by a compressed or stretched spring. the spring force acts in the opposite direction of the stretching or compression to bring the spring back to equilibrium.

applied force - F_a

a force applied to an object by another object

gravitational force - F_g

the force that pulls objects toward the center of the other massive objects(like planets). F_g is equal to an (object’s weight * g) and is always directed downward toward the center of the earth or other planet

normal force - F_n

a support force exerted on an object when it is in contact with another stable surface like a table, this force acts on the object perpendicular to the surface it is in contact with

force

vector quantity measured in Newtons(N) that causes a change in acceleration (change in velocity). Net Force is equal to the sum of all the forces acting on an object. Not required to keep an object in motion or constant velocity only to make it accelerate

balanced forces

when all the forces acting on an object cancel out or there are no forces at all

unbalanced forces

object is accelerating, forces don’t cancel out (Net Force doesn’t = 0), change in velocity

Inertia

NOT A FORCE, a tendency for an object to reisist changes in motion, depends only on an object’s mass, more mass more inertia

Newton’s First Law: Law of Inertia

An object at rest will remain at rest and an object in motion will remain in constant velocity unless acted upon by an unbalanced force

Newton’s Third Law: Force Pairs

For every action force, there is a reaction force that is equal in magnitude and opposite in direction, this is called a force pair.

• N3L force pairs don’t cancel out because they act on different objects

• The force pair to an object’s weight is the gravitational force of the object pulling on the earth

• force pair to gravity is always gravity, NOT NORMAL FORCE

internal force

interactions that produce forces within a defined system that cancel out

external force

interactions and forces that are caused by objects outside the system boundry. if these forces are not balanced, the system will accelerate.

static friction

frictional force that prevents an object from moving

kinectic friction

the frictional force that opposes motion once an object is moving

friction vs applied force graph

weight

mass * g(accel due to grav)

mass

amount while weight is a force

momentum (p)

mass in motion (vector) - kg * m/s

impulse (I)

a force applied to an object for an amount of time that results in a change in a momentum (vector) - N * s

conservation of momentum

for collisions, the total initial momentum of a system before a collision will be equal to the total final momentum of a system when there are no other forces present

• if there are any external forces other than collision, momentum is not conserved

• both objects experience the same change in momentum/impulse/force during and after the collision

• the smaller mass object experiences the greater acceleration (change in velocity)

inelastic collision or hit and stick

objects collide and stick together to form a single object with combined mass and shared velocity “bug hits windshield”

m₁ v_i + m₂ v_i = (m₁ + m₂) v_f

elastic or bounce collision

separate final velocity, not one combined object post-collision

m₁ v_{1 initial}+ m₂ v_{2 initial} = m₁ v_{1 final} + m₂ v_{2 final}

explosion

start at rest, in contact, pushed apart by “explosion,” force acts equally on both objects

(m₁ + m₂) v_i = m₁ v_{1 final} + m₂ v_{2 final}