newtons laws of motion Flashcards
What is a force?
an interaction between two objects
explain Newton’s third law
every action has an equal opposite reaction: for every force on one object there must be an opposite force on the other object in the system (RECIPROCAL FORCES! (action and reaction is kind of arbitrary, not rlly cause effect)
how does a horse pull a cart?
force on the cart forward = equal and opposite reaction on horse, but horse is a different object, thus horse only needs to overcome friction on cart
horse: backwards force of harness, then forward force from ground pushing off and equal opposite rxn therein, all the horse needs to do is generate more force from the ground than backwards force from harness’s friction in the axle of the wheel
thus; the forces on a fbd dont cancel out because theyre different objects. if you want to see if an object will move, analyze force on ONE object at a time
why do massless strings have always equal forces on either side of it?
because as the forces approach any sort of difference (sum of forces does NOT equal zero) that means that acceleration = force/0 where force does not equal zero, or in other words, creates an undefined
