Respuesta :
According to our principle, when an object is slowing down, the acceleration is in the opposite direction as the velocity. Thus, this object has a negative acceleration. ... When an object is speeding up, the acceleration is in the same direction as the velocity. Thus, this object also has a negative acceleration.
I don't know of a standard 4-step procedure for solving these problems, other than the standard procedure for solving ANY technical problem:
-- Be sure to understand the question; know exactly what it's asking for.
-- Be sure to understand exactly what information the question GIVES you.
-- Go to your toolbox: Gather all the formulas, equations, and laws you know that involve the information that's given and the answer that's to be found.
-- Pick the tools that build the best bridge between the given information and whatever has to be found.
= = = = = = = = =
Here is a good, useful, helpful, basic toolbox that everyone should carry around with them.
For the statics, dynamics, and kinematics topics that you listed, there are a few basic, fundamental tools that must be in everybody's toolbox. You really should memorize these. They'll solve at least half of all the distance and motion problems you'll ever encounter:
-- Distance covered = (mileage reading at the end of the trip) - (reading at the beginning)
-- Displacement = straight-line distance and direction from the start-place to the end-place
-- Speed = (distance covered) ÷ (time to cover the distance)
-- Change in speed = (speed at the end) - (speed at the beginning)
-- Velocity = (displacement and direction) ÷ (time for the trip)
-- Acceleration = (change in speed and direction of the change) ÷ (time for the change)
-- Distance covered from 'rest', with acceleration =
(1/2)·(acceleration)·(time squared)
= = = = =
Newton's laws & conservation:
-- Things keep moving in a straight line at constant speed, unless something makes them speed up, slow down, or curve.
-- Acceleration = (force) ÷ (mass)
-- Force ALWAYS comes in pairs. For every force, there's always another force, equal to the first one and in the opposite direction. Always.
-- Mass is conserved. It never appears or disappears. There's always the same amount after as there was before. If more shows up, it had to come from somewhere. If some disappears, it went somewhere, and you can find it if you look for it.
-- "Momentum" = (mass) · (speed)
-- Momentum is conserved. It never appears or disappears. There's always the same amount after as there was before. If more shows up, it had to come from somewhere. If some disappears, it went somewhere, and you can find it if you look for it.
-- Potential energy = (mass) · (gravity) · (height)
-- Kinetic energy = (1/2) · (mass) · (speed squared)
-- Energy is conserved. It never just appears or disappears. There's always the same amount after as there was before. If more shows up, it had to come from somewhere. If some disappears, it went somewhere, and you can find it if you look for it.
