Dynamics Flashcards
N1L
States that an object at rest will remain at rest and an object in motion will remain in motion at constant velocity in a straight line in the abscence of external resultant force
Inertia
Reluctance of a body to change its state of rest or uniform motion in a straight line
Mass
Measure of a body’s resistance to change in velocity
Weight
Force acting on a mass due to gravitational field
Why do ppl feel weightless
No contact force, eg astronaut traveling in space
Linear momentum
Linear momentum of a body is the product of the mass and its velocity. The linear momentum is in the same direction as its velocity
p=mv
N2L
States that the rate of change of momentum of a body is directly proportional to the resultant force and occurs in the direction of the resultant force
(delta p/delta t)=F
N3L
States that if body A exerts a force on body B, then body B exerts a force of the same type that is equal in magnitude and opposite in direction on body A
Impulse
Defined as the product of a force F acting on an object and the time delta t for which the force acts
Impulse=F(delta t)
Also area under F-t graph
Principle of Conservation of Linear Momentum
States that the total momentum of a system remains constant provide no external resultant force acts on the system
Difference between Elastic, Inelastic & Perfectly inelastic collisions
Elastic: Total momentum conserved, KE constant
Inelastic: Total momentum conserved, KE not constant
Perfectly inelastic: Total momentum conserved, KE not constant (stick tgt)
Difference in KE is due to dissipative forces
Useful formulas
m1u1+m2u2=m1v1+m2v2
u1-u2=v2-v1 (only for elastic collision)
Special cases for 1D elastic collisions
1. m1=m2 u1=u, u2=0 -> v1=0,v2=u Simply exchange velocities 2. m1 << m2 u1=u, u2=0 -> v1=-u,v2=0 Reversed 3. m1>>m2 u1=u,u2=0 -> v1=u,v2=2u
