Newton's Second Law of Motion Applied to Fixed Masses Flashcards
from netwons first law, if you were to push a stationary or moving rock in space, how would they react
- as a resultant force has been exerted on the stationary rock it ill being moving in the direction of the exerted force
- while the moving rock would have its velocity increase, decrease or change direction
what is the change in the momentum of the rock called when an external resultant force is exerted on it
an impulse force
what is the proper expression for an impulse force
sigma F = delta mv / delta t
what does that equation represent
the general version of newtons second law of motion
how does that equation turn into the simpler equation more commonly known for newtons second law
- as you are dealing with fixed masses, you can say there is no change of it in the momentum part of the equation, meaning only the velocity changes
- so the equation can be written as sigma F = m delta v delta t
- as change in velocity over a time interval is what acceleration is, the equation can be rewritten
- to sigma F = ma
what does newtons second law of motion, for fixed masses, then state
- the acceleration of a body of constant mass is directly proportional to the resultant force applied to it
- and the direction of the resultant force
an engine pulls three carriages along a track. the forward force of the track on the wheels of the engine drives it forwards. what condition will need to be met if the train wants to accelerate
- driving force need to exceed the resistive force
- so that there is an imbalance between the forces in opposite directions in favor of the forward force
- making the train accelerate
the driving force of the track wheels, D, acts in the forwards and opposite direction from the total resistive force fore, F, of the engine and three carriages. how could you write an equation to find the resultant force with these variables if you fit them into newtons second law
- using F = ma
- D - F = (m of engine + m of 3 carriages) x a
although the engine and the carriages accelerate at the same rate as they are attached, what is the main difference between them
the carriages have no driving force
what would the free body force diagram of the carriage look like
- you would have the tension from the carriage ahead pointing forwards, T1
- the acceleration of the carriage pointing forwards, a
- the tension from the carriage behind pointing backwards, T2
- and the other resistive forces pointing backwards, Fc
the carriage is accelerating like the rest of the train so it is experiencing a resultant force. how would you apply newtons second law of motion equation to show how its free body force diagram variables would show this
T1 - (T2 + Fc) = m of carriage x a
why do both of the equations you have written for the train and carriage have specific calculations for F
- because the F is a resultant force
- aka the sum of the forces acting on an object with direction taken into consideration
- which is why it is more technically accurate to use sigma before it
- so the resultant force is calculated first which is why there are calculations for F
what is the difference between a body and a system
- a body is isolated and so can the forces acting on the body
- whereas a system includes the interaction of bodies
