Momentum and Newton's Law Flashcards
what is newtons second law
- F=ma
- specifically, the resultant force acting on an object is directly proportional to the rate of change of linear momentum of the body
how do you get that the resultant force equals the change in momentum over the time interval the change takes place in, using newtons second law
- a = (v - u) / t
- F = ma
- F = m(v - u) / t
- so F = mv - mu / t
how would you rearrange that equation to calculate the impulse of an event
F delta t = delta mv
what does that equation imply about the relationship between the impulse force of a system and the change in momentum
they are equal in a close system
what is the unit for impulse (F delta t)
- Ns or kgms-1
- as it does equal momentum
if two ice skaters push each other apart as they move horizontally across the ice, how do both of their momentums change if it must be conserved in the system
- the change of momentum of the woman must be equal and opposite to the change in momentum of the man
- in order for the momentum of the system after the event to be equal to before the event
what does this therefore imply about how their impulse forces change
- the impulse force of the woman must be equal and opposite to the mans
- as they are equal to the change in momentum
how would you mathematically show that the man and womans forces acting on each other are equal and opposite using the equation for impulse
- the time interval of this event occurring is the same for both skaters
- so t is equal
- and as they are exerting forces in opposite directions (or have momentums directed in opposite directions)
- F delta t = -F delta 1 (man and woman)
- you can cancel the t as it is the same to get F = -F
- showing the forces they exert are equal and opposite
what does this formula prove
- newtons third law
- that when two objects interact, they exert equal and opposite forces on each other
