Momentum and Impulse Flashcards
What is an elastic collision?
Momentum and kinetic energy conserved
What is an inelastic collision?
Momentum conserved, kinetic energy dissipated
What is force?
Rate of change of momentum
What is impulse?
Change in momentum
What is Newton’s First Law?
An object will remain at constant velocity or at rest unless a net force acts on it
What is Newton’s Second Law?
The rate of change of momentum of an object is directly proportional to the net force which acts on the object.
Why can’t we always use F=ma to define the second law?
Because it assumes mass stays constant, which isn’t true when things are travelling very fast. Momentum takes into account velocity and mass changes.
What is Newton’s Third Law?
Every force has an equal and opposite reaction force. If B exerts force on A, A exerts equal and opposite force on B.
How are car features designed?
To slow you down gradually, which decreases force due to F=p/t
How do crumple zones help?
Areas at front and back of car that crumple on impact. They absorb KE and increase time taken for car to slow down.
How do seatbelts help?
Hold the wearer in place, absorbing KE by stretching, increase time take for wearer to stop
How do air bags help?
increase time taken for person to stop, stop person from hitting dashboard/wheel
How can seatbelts be dangerous?
If person is small can sit across their neck or not secure them properly. Can cause bruising.
How can air bags be dangerous?
If not wearing seatbelt, person can hit airbag as it is inflating and die. Dangerous with rear-facing car seats, as it can inflate behind child.
What is momentum?
A vector, the product of an object’s mass and velocity.
