Key Terms
When mass is constant
Delta-p = m * delta-v So F_net = m * (delta-v / delta-t) = ma That's where F = ma comes from.
Or written out
M1*v1 + m2*v2 = m1*v1' + m2*v2'
Example
A projectile in flight.
Elastic collision
Conserves both momentum AND kinetic energy
TWO CONSERVATION EQUATIONS (both must hold)
1. m1*v1 + m2*v2 = m1*v1' + m2*v2' (momentum) 2.
Pattern
Small hits large (large at rest)
Small object
Bounces back (negative final velocity) Large object: moves forward with low speed Total KE: unchanged (verify by calcula
Inelastic collision
Conserves momentum; KE is not conserved
Perfectly inelastic
Objects stick together after collision. This loses the MOST kinetic energy possible while still conserving momentum.
POINT MASSES
The source assumes point masses — structureless particles that can't rotate. This avoids the complication of rotational
Linear momentum
P = mv; vector; units kg·m/s
Impulse
F_avg * delta-t = delta-p; change in momentum
Conservation of momentum
Total momentum constant when F_net = 0
Isolated system
System where net external force = 0
Perfectly inelastic collision
Objects stick together; maximum KE loss