1247 II Flashcards
Newton’s 1st law
An object either remains stationary or continues to move with constant velocity unless acted on by an external force
Newton’s 2nd law
Net force on an object is equal to the rate of change of linear momentum
Newton’s 3rd law
every action has an equal and opposite reaction
What is meant by centre of mass frame?
Inertial frame in which the centre of mass of the system is at rest hence total momentum of system vanishes in COM frame
What is the condition for a force that depends on posn to be conservative?
If force is only dependent on posn => conservative force if work done is independent of path taken
What is meant by a central force?
A force whose magnitude only depends on distance r of object from origin
State the work-kinetic-energy theorem.
Work done is equal to change in KE: W=K(t2)-(t1)
What is the defining characteristic of SHM?
Restoring force is proportional to displacement (linear or angular)
Define the coefficient of restitution e in an elastic collision.
Ratio of speeds before and after collision.
What are conserved for central force?
Angular momentum and energy
What is the potential for a stable circular orbit?
Effective potential is min.
What is meant by centripetal acceleration?
Accn that acts towards centre & is required for tangential velocity to have a constant mag. but different direction
Why is Newton’s first law just a special case of the second?
It is the special case when F=0.
Describe underdamped motion.
Underdamped: The system oscillates (at reduced frequency compared to the undamped case) with the amplitude gradually decreasing to zero.
Describe critical damping.
Critically damped: The system returns to equilibrium as quickly as possible without oscillating.
