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Module 3 - Chapter 7 - Laws of Motions and momentum - Coggle Diagram
Module 3 - Chapter 7 - Laws of Motions and momentum
Newton's laws of motion
First Law
If velocity changes, resultant force must have acted on the object
An object will remain at rest or continue to move with constant velocity unless acted on by a resultant force
Third Law
When two objects interact, they external equal and opposite forces on each other
Pair of forces produced when two objects interact will always be equal in magnitude and opposite in direction and of the same type
Fundamental forces
Gravitational
Electromagnetic
Strong nuclear
Weak nuclear
Second law
Resultant force acting on an object is directly proportional to the rate of change of its momentum
Net force is proportional to the rate of change of momentum
K is made equal to 1 by defining the newton as the force required to give a 1kg mass an acceleration of 1 m/s
F = ma
Special case of Newton's second law when the mass of object remains constant during acceleration
Momentum
Momentum = mass x velocity
Conservation
When two objects collide/ interact, objects transfer momentum and kinetic energy between themselves.
Principle of conservation of momentum - For a system of interacting objects, total momentum in a specified direction remains constant, as long as no external forces act on the system
Group of interacting objects is a closed system
Total momentum before and after a collision is constant
Why?
3rd law state each object experiences an equal but opposite force
Net force acting on the objects in this closed system in zero
Change in momentum for both objects is 0
Total momentum of the objects doesn't change, momentum is conserved
Investigating momentum
Linear air track is ideal because a cushion of air minimizes the friction between trolley's and track
Velocity of each object is determined with a motion sensor, light gates, data logger, and digital timer
Elastic/ inelastic collisions
Perfectly elastic collisions
Momentum is conserved
Total energy is conserved
Total kinetic energy isn't conserved
Inelastic
Momentum is conserved
Total energy is conserved
Total kinetic energy isn't conserved
All kinetic energy could be retained by the objects, or it could be transformed into other forms like heat/sound
Impulse
Forces accelerating or decelerating an object change over time. This type of motion can be analysed using the idea of an impulse
Rearranging newton's second law
Impulse of a force = product of the force and the time for which thise force acts on an object
Impulse of a force = change in momentum
Unt is Ns of Kgms^-1
Force time graphs
Area under the graph is the impulse of the force or change in momentum
Collisions in 2D
Adding momentum
Moving object A collised with stationary object B
After the collisions, A and B move off in different directions
Linear momentum must be conserved, the vector sum of individual momentum must equal the initial momentum
Vector triangle can be draw to add vectors together
Resolving momentum
Momentum in any direction must be conserved
Momentum must remain the same in the x direction and y direction
Total initial momentum = total final momentum
