Dynamics Flashcards
Newton’s 1st Law.
Body will remain at rest or continues to move with uniform velocity unless a resultant force acts on it [Inertia]
Newton’s 2nd Law.
Rate of change of momentum of a body is proportional to resultant force acting on it and take places in the same direction [F=ma]
Newton’s 3rd Law.
If body A exerts a force on body B, body B will exert a force of the same type and magnitude but in opposite direction on body A.
Conditions when identifying action-reaction forces
When will forces cancel out?
- Equal in magnitude, opp. direction
- Same type of force
- 2 different bodies
When they act on the same body
Definition and formula for linear momentum
Linear momentum is peoduct of mass of body and its velocity.
p=mv
2 things to note when drawing FBD.
- Weight acts directly downwards
2. Normal contact force acts perpendicular to surface
Solving qn with FBD
- Draw FBD of bodies
- N2L (f=ma) of bodies/whole system
- Keep in mind N3L [Fab = Fba, opp. direction]
What is impulse?
How to find impulse?
Change in momentum (△p)
a) △p = △t x Fnet
b) Area under Fnet - t graph
Tackling qns involving impulse.
- △p = Ft = mv-mu
2. Let t=1s
Principle of Conservation of momentum?
Equation relating to COLM
Net momentum of system remains constant provided no external resultant force acts on system
Total momentum before collision = Total momentum after collision
m1u1 + m2u2 = m1v1 + m2v2
Elastic vs inealstic collision?
Elastic –> Total KE remains the same
- COLM + (RSA = RSS)
Inelastic –> Total KE not conserved [All real collisions]
- COLM
General formula for RSA = RSS?
Refer to image 1
Special cases for COLM.
1) Coalesce (Perfecty inelastic)
- Stick together
- Final velocity same (v1 = v2)
2) Seperation (‘Explosion’)
- Both bodies stationary at start
- u1 = u2 = 0
- Momentum of system = 0
