dynamics Flashcards
super glossary
what is newtons first law
the law of inertia which means that an object at rest will remain at rest and an object in motion will remain in motion unless acted upon by a net external force
what is newtons second law
newtons second law can be described by the equation
force=mass x acceleration
this equation show that the acceleration is proportional to the resultant force of an object and inversely proportional to the mass
what is newtons third law
when two object interact the exsert an equal and opposite reaction on each other
acceleration
its a vector and is the rate of change of a velocity
average velocity
the rate of change of displacement over a finite time
instantaneous velocity
the instantaneous rate of change of displacement ( over a infinite time)
conservation of energy
the principle of conservation of energy is that “ energy cannot be created or destroyed it can change form but the total amount of energy in a closed system never changes
crumple zone
an area of a car designed to fail plastically in the event of a car crash turning kinetic energy into heat and so reducing the kinetic energy imparted to the bodies reducing the recoil velocity.
this results in a lower change in momentum as by Neutons second law a lesser force exerted on the bodies.
another way to think of this is that the crumple zone increases the duration of the crash reducing the rate of change of velocity required and so reducing the change in momentum
displacement at time
(vector) distance in a direction from the time of 0
drag
resistive force exserted by a fluid on a body moving through that fluid
efficiency
the ratio between useful energy transferred and total energy transferred
elastic collision
a collision in which kinetic energy is conserved
equilibrium
result forces acting on it are 0
freefall
falling with little air resistance (i.e.. the bit between jumping and opening your parachute)
friction
a force that opposes motion. however motion isn’t at all needed a brick on hill with be experiencing a frictional force upwards whether it is moving or not
gravitational potential energy
the energy an object ( or more specifically a system) has because of it position in a gravitational field ( or more strictly because of the distance between the two object that exert gravitational forces on each other. numerically the same a the work done to move that object to its position in the gravatiational feild
impulse
change in momentum equal to force x time equal to the time the area under a force time graph
kinetic energy
energy a body has by virtue of its movement
lift
a force caused by a body passing through a liquid typically upwards
mass
the amount of matter in an object. mass can be “inertial mass” ie a force must act on it to change its momentum, or “gravitational mass” ie a the property of the body exerts a gravitational force on the bodies around it
momentum
the momentum of a body is the product of that’s bodies mass and velocity.
momentum is conserved so the total momentum before an event is the same as after an event.
it is also a vector
power
rate of transfer of energy
projectile motion
motion of a body with horizontal component of velocity that remains constant because there are zero or negligible horizontal forces acting on the body and a vertical component of velocity that changes uniformly with time because the only non- negligible vertical force acting n the body is weight. the curve produced by the path of the body in the vertical plane is called a “parabolic” curve or a parabola
resultant force
net force acting on a object
scalar
a quantity with a magnitude only
tangent
a line draw on a a curve that is parallel to the point on that curve
often on a graph the gradient of the tangent ( on a displacement time graph gives the instantaneous velocity) and ( on a velocity time graph the gradient gives instantiations acceleration)
terminal velocity
the maximum speed/ velocity a body can reach when falling through a liquid
terminal velocity is reached when drag is equal to weight in opposite directions to resultant force is 0
vector
a quantity with magnitude and direction
weight
the force exerted on a mass by a gravitational field
