C7 - Laws of Motion and Momentum Flashcards
What is Newton’s second law of motion?
The resultant force acting on an object is directly proportional to the rate of change of its momentum, and is in the same direction.
This means net force is directly proportional to the rate of change of momentum.
What is Newton’s third law of motion?
When two objects interact they exert equal and opposite forces on each other.
The pair of forces produced will always be equal and opposite and the forces acting on the interacting objects are always the same type.
E.g. Electrons have a negative charge and exert an electrostatic repulsive force on each other and experience the same magnitude of force but in opposite directions.
What are the four fundamental forces of all interactions?
Gravitational forces
Electromagnetic forces
Strong nuclear forces
Weak nuclear forces
Why can equation F = mA not be used to predict the motion of a rocket?
Because the mass of the rocket decreases as it is fuel is consumed and expelled therefore momentum must be used
How is momentum calculated?
Momentum = mass * velocity p = mv
It’s a vector quantity
What is the principle of conservation of momentum?
For a system of interacting objects the total momentum in a specified direction remains constant as long as no external forces act on the system.
This means that when objects collide the total momentum before and after the collision is the same.
What is an elastic collision?
One where momentum, total energy and total kinetic energy is conserved
What’s am in elastic collision?
One where momentum and total energy are conserved but total kinetic energy is not conserved and is transferred into different forms of energy.
How can an equation for newtons second law be written?
Net force = change in momentum / change in time
F = Δp / Δt
What is the impulse of a force?
The change in momentum
The area under a force-time graph is always equal to the change in momentum
How can the momentum of linear collisions be calculated?
Are using vector triangles
How can the total momentum be resolved in the X and Y direction?
(Of an object moving right and colliding with another)
Total initial momentum = total final momentum
X direction:
m1v0 = m1v1Cos°1 + m2v2Cos°2
Y direction:
0 = m1v1Sin°2 + m2v2Sin°2
What is Newton’s first law of motion?
An object will remain at rest or continue to move with constant velocity unless acted upon by resultant force.
If an object is velocity changes then you know a resultant force must be acting on the object.
What is Newton’s first law of motion?
An object will remain at rest or continue to move with constant velocity unless acted upon by resultant force.
If an object is velocity changes then you know a resultant force must be acting on the object.
What is Newton’s second law of motion?
The resultant force acting on an object is directly proportional to the rate of change of its momentum, and is in the same direction.
This means net force is directly proportional to the rate of change of momentum.
